[Core] Deprecate Split Transaction status field

[KarlK90]

Description

It is a left over from previous serial implementations like the helix keyboard. The field is read and written to in split communications, but never evaluated as the current core implementation relies on the return value of soft_serial_transaction which is treated as a bool anyways. Therefore status is removed and soft_serial_transaction returns a bool now.

soft_serial_get_and_clean_status is removed as well as it is dead code.

Size impact

AVR: -202 Bytes

./util/size_regression.sh -d maintenance/deprecate-transaction-status crkbd:default
Size:    27572, delta:   -202 -- 2582edb1da Deprecate split transactions status field

ARM: +96 Bytes

./util/size_regression.sh -d maintenance/deprecate-transaction-status zvecr/zv48/f411:default
Size:    34352, delta:    +96 -- 2582edb1da Deprecate split transactions status field

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• Actually frees about 200 bytes on AVR splits where space is already tight

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[drashna]

Doesn't seem to break anything, at least on ARM.