Feature: Add support for SYS_ELAPSED/SYS_TICKFREQ as milliseconds

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Detailed description

• This is a small new feature.
• The existing problem is BMD not supporting semihosting calls 0x30 SYS_ELAPSED, 0x31 SYS_TICKFREQ.
• This PR solves it by providing small implementations giving out platform time in milliseconds, conforming to ARM ABI. https://github.com/ARM-software/abi-aa/blob/main/semihosting/semihosting.rst

Tested on blackpill-f411ce platform with extra diagnostic logging against gd32f303cc-bluepillplus running a modified instance of blackmagic-test-fw-archive semihosting project (to avoid exiting early on errors). Stop-the-world delay observed by target is around 19ms in JTAG mode at max frequency for each syscall handled in-probe, no USB or GDB communication. SWD might be faster. Also tested on BMDA+BMP for a delay of 133ms (I am subtracting the in-sketch delay(50)).

Your checklist for this pull request

• [x] I've read the Code of Conduct
• [x] I've read the guidelines for contributing to this repository
• [x] It builds for hardware native (see Building the firmware)
• [x] It builds as BMDA (see Building the BMDA)
• [x] I've tested it to the best of my ability
• [x] My commit messages provide a useful short description of what the commits do

Closing issues