travis: Drop testing Python 3.5 and 3.6 ...

A few libraries we depend on no longer support old versions of Python
like 3.5 and 3.6. Remove testing for these old versions.

travis: Use latest pip ...

As we depend on the cryptography library, and the pip version that comes
with Ubuntu Focal isn't new enough to avoid the following error about a
rust compiler and pre-built wheels, ensure Travis uses an up-to-date
pip.

    error: can't find Rust compiler

    If you are using an outdated pip version, it is possible a prebuilt wheel is available for this package but pip is not able to install from it. Installing from the wheel would avoid the need for a Rust compiler.

    To update pip, run:

        pip install --upgrade pip

travis: Remove trailing whitespace

Merge pull request #14701 from donatieng/utf-8-check ...

Add Travis test to make sure text files are UTF-8 encoded

Add Travis test to detect any non-UTF-8-encoded text

Travis: Do not ignore deleted frozen files ...

The filter `--diff-filter=d' causes deleted files to be ignored from
the frozen tools check. But there is no reason for this, as deleting
a file can break compatibility with the legacy tools.

Travis: Fix frozen tools check never failing ...

Having recently moved the frozen tools check to a standalone stage
at the end, we need to fetch the base branch so make comparison
work. Travis environments are not shared across different stages.

Without the fetch, the check always passes as a PR is compared with
itself.

Travis: Use shallow fetches ...

We only compare files in current PR with the base branch. There's no
need to fetch the full git history or branches that are not involved
in the comparison.

This is to save time in Travis runs.

Travis: Move frozen tools check to the end ...

When the scripts for the old tools are modified (e.g. when a new
target is added), the frozen tools check fails but we allow the change
if it's really needed. By moving the frozen tools check to the end,
Travis doesn't terminate early and the other tests get to run.

CMake: Run the unit tests in travis CI

Travis: Add kitware repository to source list ...

The default distribution of CMake that comes with focal is 3.16.3. Add
kitware's repository (https://apt.kitware.com/) to the source list so
the latest copy of CMake is installed during CI.

Remove redundant ninja-build from apt packages

Cmake: Add backward compatibilty support for MBED_TEST_MODE ...

Fixes #14494

MBED_TEST_MODE is required for backward compatibilty with CLI1. This
adds a test to ensure that the macro is created when using CLI2 for
testing. This also adds a test in `.travis.yml` that checks whether
CMake defines the macro when BUILD_TESTING is on.

CLI1 Reference: https://os.mbed.com/docs/mbed-os/v6.9/debug-test/greentea-for-testing-applications.html

Also, explicitly create and set the macro BUILD_TESTING to allow for
MBED_TEST_MODE to be defined by CMake. MBED_TEST_MODE is required for
backward compatibilty with CLI1.  BUILD_TESTING is used to determine
whether to define MBED_TEST_MODE.  Normally, this would be automatically
done by CTest (which we intend to add for test automation) but this
hasn't yet been added to our Greentea tests.

Travis: use addons to install libncursesw5

Travis: deprecate python 2.7 ...

Python 3, it's your time now

fixup! aspell: fix dependencies missing

fixup! aspell: fix dependencies missing

Travis: remove littlefs generic tests ...

They do not add any value as littlefs library contains own tests, we do not need to duplicate them in Mbed OS.
We test integration with our libraries.

Travis: update to 20.04 ...

Updating to the latest Travis provided environment. It's been a year around and we can benefit from
more updated versions we use.

More info https://docs.travis-ci.com/user/reference/focal/

Update PinNames markers

Add standard pin-names validation script & tests

Travis: Remove make.py test for events and littlefs ...

The removed tests were building applications from the content of their
respective README files. The events test was building with the full profile twice.
The first time with the repository as is; and the second time after deleting
some directories (to simulate the baremetal profile).
The littlefs test was building once with the full profile.

Testing make.py is no longer required as it is no longer supported.
There is already test coverage for APIs in the removed tests.

travis: fix 3.5 test bug in attrs ...

Using specific version (pre 20) should fix the issue https://github.com/ARMmbed/mbed-os/issues/14110

Moved USB drivers under drivers/usb

Activate ccache for CMake

TEST: remove cmake build test from TravisCI

CMake: Fix travis fetch PR (#13763) ...

Either fetch TRAVIS_COMMIT or the entire pull request (depending on the TRAVIS_PULL_REQUEST environment variable).

CMake: Replace tested BLE application in CI description ...

BLE_Button, which was the previously tested BLE example, is
being removed in mbed-os-example-ble. Replace it with BLE_LED.

Travis: add more examples we should support ...

Co-authored-by: Hugues Kamba <41612201+hugueskamba@users.noreply.github.com>

CMake: Check CMake builds CMake-capable targets in Travis