lib/search/, lib/, src/: Add a type parameter to the type-safe macros

lib/search/, lib/, src/: Add a type parameter to the type-safe macros

This simplifies the implementation, allowing us to use _Generic(3) to
replace _Static_assert(3), is_same_type(), and local variables.

Local variables in macros can cause issues when nesting such macros.

This also makes the code more readable, by having the type explicitly
stated at call site.

Signed-off-by: Alejandro Colomar <alx@kernel.org>