Flag: --incompatible_force_strict_header_check_from_starlark

Prevents use of the legacy loose header checking mode from Starlark.
See #11677 for details.

Migration

This is an incompatible change because it may break rules under obscure circumstances; if this happens then ensure all required headers are explicitly specified to the relevant targets.

This is only observable with the sandbox disabled, so more likely to be seen on Windows.