Add initial Mbed CE support for Ambiq Apollo3

[multiplemonomials]

Summary of changes

This PR is the result of the first round of testing I did with my new Ambiq Apollo3 board (SFE_ARTEMIS). It adds initial Mbed CE support for the board, including a rewritten linker script, an upload method configuration file, and a bugfix to the Greentea test runner so it can work with this MCU.

I also ran a full greentea run with this board, and all greentea tests (that are currently set up and are enabled for this target) now pass! Fixed two issues with the lp ticker.

Impact of changes

• SFE Artemis now has an upload method configuration
• Ambiq Apollo3 lp ticker and us ticker no longer have an issue where they can fire unexpectely when set, disabled, and then reset
• Ambiq Apollo3 lp ticker clock now turned off in deep sleep mode
• Ambiq Apollo3 linker script now supports memory bank configuration
• Some old unused code in Mbed removed
• lp and us ticker API documentation now clearer about a few specific points
• additional regression tests added in common-tickers test to better screen for this type of issue
• --sync-predelay option added to Greentea
• Greentea test runner bug fixed where sync word did not get properly retried

Migration actions required

Documentation

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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

100% tests passed, 0 tests failed out of 116

Total Test time (real) = 519.24 sec

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