[analyzer] Add option for AddrSpace in core.NullDereference check

    This change adds an option to detect all null dereferences for
    non-default address spaces, except for address spaces 256, 257 and 258.
    Those address spaces are special since null dereferences are not errors.

    All address spaces can be considered (except for 256, 257, and 258) by
    using -analyzer-config
    core.NullDereference:DetectAllNullDereferences=true. This option is
    false by default, retaining the original behavior.

    A LIT test was enhanced to cover this case, and the rst documentation
    was updated to describe this behavior.

Reviewed By: steakhal

Differential Revision: https://reviews.llvm.org/D122841