fix Issue 11489, add cast from const(LocalTime) to immutable
Merge pull request #1689 from 9rnsr/fix11489

fix Issue 11489, add cast from const(LocalTime) to immutable
Introduce package level `canSearchInCodeUnits`

And use it to solve bugs/simplify code.
Merge pull request #1517 from monarchdodra/fitsInCodeUnit

Fix bugs using `fitsInCodeUnit`