We should always have a T_HASH here, so we can use FL_TEST_RAW to avoid
checking whether we may have an immediate value.

I expect this to be a very small performance improvement (perf stat
./miniruby benchmark/hash_aref_miss.rb shows a ~1% improvement). It also
removes 9 instructions from rb_hash_default_value on x86_64.

On a hash miss we need to call default if it is redefined in order to
return the default value to be used. Previously we checked this with
rb_method_basic_definition_p, which avoids the method call but requires
a method lookup.

This commit replaces the previous check with BASIC_OP_UNREDEFINED_P and
a new BOP_DEFAULT. We still need to fall back to
rb_method_basic_definition_p when called on a subclasss of hash.

    |                |compare-ruby|built-ruby|
    |:---------------|-----------:|---------:|
    |hash_aref_miss  |       2.692|     3.531|
    |                |           -|     1.31x|

Co-authored-by: Daniel Colson <danieljamescolson@gmail.com>
Co-authored-by: "Ian C. Anderson" <ian@iancanderson.com>
Co-authored-by: Jack McCracken <me@jackmc.xyz>

One year ago, the former method has been deprecated while the latter
has become an error.  Then the 3.1 released, it is enough time to make
also the former an error.

rb_ary_tmp_new suggests that the array is temporary in some way, but
that's not true, it just creates an array that's hidden and not on the
transient heap. This commit renames it to rb_ary_hidden_new.

[Misc #18891]