gccrs: format-parser: Add `is_some_and` method for Option<T>

Workaround for Ubuntu 18.04, since we still use it for the GCC 4.8 CI.
The default Rust package is 1.65 (and unlikely to change I assume?),
but the generic format parser library uses `is_some_and` which was
introduced in 1.70. So this is a simple reimplementation, directly taken
from the standard library sources.

libgrust/ChangeLog:

	* libformat_parser/generic_format_parser/src/lib.rs: Add IsSomeAnd<T>
	trait, impl it for Option<T>.