add opsi driver

Remove usage of UARTSerial in Mbed OS Core diretories ...

Replace with BufferedSerial as UARTSerial has been deprecated.

Revise MbedCRC template ...

* Use compile-time detection of hardware CRC capability, so unneeded
  code and tables do not go into the image.
* Add global JSON config option to allow choice between no tables,
  16-entry tables or 256-entry tables for software CRC. Default set
  to 16-entry, reducing ROM size from previous 256-entry.
* Allow manual override in template parameter to force software or
  bitwise CRC for a particular instance.
* Micro-optimisations, particularly use of `RBIT` instruction and
  optimising bitwise computation using inline assembler.

Incompatible changes:

* Remove special-case "POLY_32BIT_REV_ANSI" - users can use standard
  POLY_32BIT_ANSI, which now uses the same 16-entry tables by default,
  or can use hardware acceleration, which was disabled for
  POLY_32BIT_REV_ANSI. MbedCRC<POLY_32BIT_ANSI, 32, CrcMode::TABLE> can
  be used to force software like POLY_32BIT_REV_ANSI.
* The precomputed table for POLY_16BIT_IBM had errors - this has been
  corrected, but software CRC results will be different from the previous
  software calculation.
* < 8-bit CRC results are no longer are shifted up in the output value,
  but placed in the lowest bits, like other sizes. This means that code
  performing the SD command CRC will now need to use `(crc << 1) | 1`,
  rather than `crc | 1`.

Revert "MbedCRC and CRC HAL revisions"

Revise MbedCRC template ...

* Use compile-time detection of hardware CRC capability, so unneeded
  code and tables do not go into the image.
* Add global JSON config option to allow choice between no tables,
  16-entry tables or 256-entry tables for software CRC. Default set
  to 16-entry, reducing ROM size from previous 256-entry.
* Allow manual override in template parameter to force software or
  bitwise CRC for a particular instance.
* Micro-optimisations, particularly use of `RBIT` instruction and
  optimising bitwise computation using inline assembler.

Incompatible changes:

* Remove special-case "POLY_32BIT_REV_ANSI" - users can use standard
  POLY_32BIT_ANSI, which now uses the same 16-entry tables by default,
  or can use hardware acceleration, which was disabled for
  POLY_32BIT_REV_ANSI. MbedCRC<POLY_32BIT_ANSI, 32, CrcMode::TABLE> can
  be used to force software like POLY_32BIT_REV_ANSI.
* The precomputed table for POLY_16BIT_IBM had errors - this has been
  corrected, but software CRC results will be different from the previous
  software calculation.
* < 8-bit CRC results are no longer are shifted up in the output value,
  but placed in the lowest bits, like other sizes. This means that code
  performing the SD command CRC will now need to use `(crc << 1) | 1`,
  rather than `crc | 1`.

QSPI : Define default pins at drivers level ...

Now, these pins can be used everywhere (MBED_CONF_DRIVERS_QSPI_xxx)
and be redefined in local mbed_app.json
(no more need to patch PinNames.h file)

SPI upgrade - per-peripheral mutex and GPIO-based SSEL ...

This commit takes some of the work done on the SPI class from #8445, and
refines it, to provide the per-peripheral mutex functionality.

This also implements GPIO-based SSEL, which exposes a new
select()/deselect() API for users to group transfers, and should work on
every platform (unlike the HAL-based SSEL). This requires users to use a
new constructor to avoid backwards compatibility issues.

To activate the per-peripheral mutex, the HAL must define SPI_COUNT and
provide spi_get_peripheral_name().  (In #8445 this is a reworked
spi_get_module, but the name is changed here to avoid a collision with
existing HALs - this commit is designed to work without wider HAL
changes).

Fixes: #9149

Major Refactoring & extensions ...

For keep supporting external APIs with the same name (supposedly there are a larger
number of users of those APIs), BufferedSerial and ATParser are being renamed.
BufferedSerial becomes UARTSerial, will complement a  future USBSerial etc.
ATParser becomes ATCmdParser.

* UARTSerial moves to /drivers

* APN_db.h is moved from platform to cellular/util/.

* Original CellularInterface is restored for backward compatability (again, supposedly there
  are users of that).

* A new file, CellularBase is added which will now servce as the base class for all
  upcoming drivers.

* Special restructuring for the driver has been undertaken. This makes a clear cut distinction
  between an on-board or an off-board implementation.
  	- PPPCellularInterface is a generic network interface that works with a generic FileHandle
          and PPP. A derived class is needed to pass that FileHandle.
        - PPPCellularInterface provides some base functionality like network registration, AT setup,
          PPP connection etc. Lower level job is delegated to the derived classes and various modem
          specific APIs are provided which are supposed to be overridden.
        - UARTCellularInterface is derived from PPPCellularInterface. It constructs a FileHandle and
          passes it back to PPPCellularInterface as well as provides modem hangupf functionality.
          In future we could proive a USBInterface that would derive from PPPCellularInterface and could
          pass the FileHandle back.
	- OnboardCellularInterface is derived from UARTCellularInterfae and provides hooks to
          the target provided implementation of onbard_modem_api.h. An off-board modem, i.e, a modem on
          a shield has to override the modem_init(), modem_power_up() etc as it cannot use
          onboard_modem_api.h.