Kunit to check the longest symbol length

The longest length of a symbol (KSYM_NAME_LEN) was increased to 512
in the reference [1]. This patch adds kunit test suite to check the longest
symbol length. These tests verify that the longest symbol length defined
is supported.

This test can also help other efforts for longer symbol length,
like [2].

The test suite defines one symbol with the longest possible length.

The first test verify that functions with names of the created
symbol, can be called or not.

The second test, verify that the symbols are created (or
not) in the kernel symbol table.

[1] https://lore.kernel.org/lkml/20220802015052.10452-6-ojeda@kernel.org/
[2] https://lore.kernel.org/lkml/20240605032120.3179157-1-song@kernel.org/

Link: https://lore.kernel.org/r/20250302221518.76874-1-sergio.collado@gmail.com


Tested-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Rae Moar <rmoar@google.com>
Signed-off-by: Sergio González Collado <sergio.collado@gmail.com>
Link: https://github.com/Rust-for-Linux/linux/issues/504


Reviewed-by: Rae Moar <rmoar@google.com>
Acked-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <shuah@kernel.org>