fix: backport Rails 8.1 routing keywords to release-0-9

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On release-0-9, drawing either a plural or singleton JSONAPI route under Rails 8.1 raises ArgumentError: wrong number of arguments (given 4, expected 3) in the Rails resource constructor. The calls to resource and resources also emit positional-options deprecations.

Pass the existing options as keywords at all four routing calls. This keeps the 0.9 resource and serialization contracts intact for applications upgrading Rails. Add two database-free regression tests covering plural and singleton route generation, controller options, and excluded actions.

This is a maintenance-branch backport related to #1496, which targets master; it also handles the two outer routing calls. It does not attempt the broader compatibility changes in #1480.

Validation on Ruby 3.3.8:

• Before the fix: both tests raise the constructor argument error on Rails 8.1.4.
• After the fix: 2 tests / 9 assertions pass on each of Rails 7.0.8.7, 7.1.6, 7.2.4, and 8.1.4.
• Command: ruby -Ilib -e 'v=ARGV.fetch(0); gem "railties",v; gem "actionpack",v; gem "activerecord",v; load "test/unit/routing_compatibility_test.rb"' 8.1.4 (repeat with each version in an environment containing its gems).
• The complete upstream suite and older Rails/Ruby matrix were not run. These tests establish routing compatibility only.