Fix: CMSIS-DAP packet size handling

[dragonmux]

Detailed description

This PR fixes the way the CMSIS-DAP code handles adaptor packet sizing and the differences between HID and Bulk endpoint (v1 and v2) based firmware.

Tested working against ORBTrace and picoprobe (which is based directly on the ARM reference implementation).

This finally solves the mystery too of how the packet size and buffer interact with one another and the HIDAPI code, documenting this properly.

Your checklist for this pull request

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

Closing issues

[esden]

Just found one little oddness otherwise it looks good.

[esden]

LGTM