Add a basic yield function to the scheduler

[m-m-adams]

This is a very basic yield with no context switching. It allows recalling the yielding task to match how routine for sd is used in the sd read functions, so still needs guards (if (sdRoutineLock) )

[github-actions[bot]]

Test Results

45 tests  +1   45 :white_check_mark: +1   1s :stopwatch: -1s  8 suites ±0    0 :zzz: ±0   8 files   ±0    0 :x: ±0 

Results for commit 13a3f690. ± Comparison against base commit c403ecc9.

:recycle: This comment has been updated with latest results.

[m-m-adams]

Force push was to remove the sd reading change - that belongs in #2111