Implement AMBIQ_SVL upload method for Ambiq Apollo3

[multiplemonomials]

Summary of changes

This PR adds an upload method for the Ambiq Apollo3 SVL bootloader. This lets you program SparkFun Artemis boards without the use of an external SWD programmer.

Impact of changes

• AMBIQ_SVL upload method added
• svl.py Python script is now bundled with Mbed. It is not pip installable and it's a single <500 line file, so it seemed simplest to just add it to Mbed so that the user doesn't have to manually clone it somewhere.
• All Artemis boards now have upload method config files

Migration actions required

Documentation

Will add section to upload methods page once this is ready to merge

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Pull request type

[] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[X] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[] Covered by existing mbed-os tests (Greentea or Unittest)
[X] Tests / results supplied as part of this PR

Verified that I can run Greentea using this method and everything works!

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