[Bug #20280]

Backport of #10014.

https://rubyci.s3.amazonaws.com/rhel_zlinux/ruby-3.3/log/20240528T214850Z.fail.html.gz

```
1)
Execution variable $: default $LOAD_PATH entries until sitelibdir included have @gem_prelude_index set FAILED
Expected ["/home/chkbuild/build/20240528T214850Z/mspec/lib/mspec/lib",
 "/home/chkbuild/build/20240528T214850Z/mspec/lib",
 "./ruby/tool/lib",
 "/home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/site_ruby/3.3.0",
 "/home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/site_ruby/3.3.0/s390x-linux",
 "/home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/site_ruby",
 "/home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/vendor_ruby/3.3.0",
 "/home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/vendor_ruby/3.3.0/s390x-linux",
 "/home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/vendor_ruby",
 "/home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/3.3.0",
 "/home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/3.3.0/s390x-linux"].include? "/home/chkbuild/build/20240528T214850Z/lib/ruby/site_ruby/3.3.0"
to be truthy but was false
/home/chkbuild/build/20240528T214850Z/rubyspec/language/predefined_spec.rb:885:in `block (2 levels) in <top (required)>'
/home/chkbuild/build/20240528T214850Z/rubyspec/language/predefined_spec.rb:846:in `<top (required)>'
```

It does have /home/linux1/chkbuild/tmp/build/20240528T214850Z/lib/ruby/site_ruby/3.3.0,
so it seems actually fine. It seems to be failing due to its setup
issues. Skipping this until we figure out how to fix it.

Since Ruby 3.0, Ruby has passed a keyword splat as a regular
argument in the case of a call to a Ruby method where the
method does not accept keyword arguments, if the method
call does not contain an argument splat:

```ruby
def self.f(obj) obj end
def self.fs(*obj) obj[0] end
h = {a: 1}
f(**h).equal?(h)  # Before: true; After: false
fs(**h).equal?(h) # Before: true; After: false

a = []
f(*a, **h).equal?(h)  # Before and After: false
fs(*a, **h).equal?(h) # Before and After: false
```

The fact that the behavior differs when passing an empty
argument splat makes it obvious that something is not
working the way it is intended.  Ruby 2 always copied
the keyword splat hash, and that is the expected behavior
in Ruby 3.

This bug is because of a missed check in setup_parameters_complex.
If the keyword splat passed is not mutable, then it points to
an existing object and not a new object, and therefore it must
be copied.

Now, there are 3 specs for the broken behavior of directly
using the keyword splatted hash.  Fix two specs and add a
new version guard. Do not keep the specs for the broken
behavior for earlier Ruby versions, in case this fix is
backported. For the ruby2_keywords spec, just remove the
related line, since that line is unrelated to what the
spec is testing.

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

[Feature #19755]

Before (in /tmp/test.rb):

```ruby
Object.class_eval("p __FILE__") # => "(eval)"
```

After:

```ruby
Object.class_eval("p __FILE__") # => "(eval at /tmp/test.rb:1)"
```

This makes it much easier to track down generated code in case
the author forgot to provide a filename argument.