YJIT: End the block after OPTIMIZE_METHOD_TYPE_CALL (#13245)

	Refactor RUBY_DESCRIPTION assertions in test_rubyoptions

[Bug #20585]

This was changed in 36a06efdd9f0604093dccbaf96d4e2cb17874dc8 because
`String.new(1024)` would end up allocating `1025` bytes, but the problem
with this change is that the caller may be trying to right size a String.

So instead, we should just better document the behavior of `capacity:`.

Co-authored-by: Jean Boussier <jean.boussier@gmail.com>

	[Bug #20322] Fix rb_enc_interned_str_cstr null encoding

	The documentation for `rb_enc_interned_str_cstr` notes that `enc` can be
	a null pointer, but this currently causes a segmentation fault when
	trying to autoload the encoding. This commit fixes the issue by checking
	for NULL before calling `rb_enc_autoload`.

This is a C API for extensions to resolve and get function symbols of other extensions.
Extensions can check the expected symbol is correctly loaded and accessible, and
use it if it is available.
Otherwise, extensions can raise their own error to guide users to setup their
environments correctly and what's missing.

We want to make sure that if preregister is called with different data,
that the postponed job table is updated.

... to disable a warning: assigned but unused variable - expected