It is not "in bytes" for wide char literal.

[Feature #20205]

Now that chilled strings no longer appear as frozen, there is no
need to offer an API to check for chilled strings.

We however need to change `rb_check_frozen_internal` to no
longer be a macro, as it needs to check for chilled strings.

Signed-off-by: crazeteam <lilujing@outlook.com>

Some extensions (like stringio) may need to differentiate between
chilled strings and frozen strings.

They can now use rb_str_chilled_p but must check for its presence since
the function will be removed when chilled strings are removed.

[Bug #20389]

[Feature #20205]

Co-authored-by: Jean Boussier <byroot@ruby-lang.org>

Signed-off-by: cui fliter <imcusg@gmail.com>

Already these had been announced to be removed in 3.2.

Presence of RBIMPL_ATTR_NONNULL let C compilers to eliminate
must_not_null().  Because null pointers are not allowed to exist there
are no reason to call the function.  In reality null pointers are still
passed to those functions in a number of ways.  Runtime check for them
are definitely nice to have.  fix [Feature#18280]

I was not aware of this because I use clang these days.

Must not be a bad idea to improve documents. [ci skip]