chore: Add Ruby 4.0 to CI

[aandreassa]

Adding specific gems as they were unbundled from Ruby 4.0:

.../windows.rb:1: warning: fiddle/import is found in fiddle, which is not part of the default gems since Ruby 4.0.

Pinning to these specific versions due to CI constraints.

ostruct 0.5.5 is required due to:

The source contains the following gems matching 'ostruct':

  * ostruct-0.5.5

	from /opt/hostedtoolcache/Ruby/3.2.11/x64/lib/ruby/3.2.0/bundler/resolver.rb:357:in `block in prepare_dependencies'

	from /opt/hostedtoolcache/Ruby/3.2.11/x64/lib/ruby/3.2.0/bundler/resolver.rb:342:in `each'
       ...

Similarly for fiddle.

Fixes #26615