…loads/branches/ (#2086)

* Minimum Ruby version is non-EOL per https://www.ruby-lang.org/en/downloads/branches/ (#2086)

* Only support current Rails and Ruby

In further review of the end-of-life dates for Ruby and Rails,
I propose that we target Ruby >= 3.2 and Rails >= 7.1 which will
be the lowest actively supported versions on April 1, 2025. We can
ship v4 on that date.

* remove backwards compat carve-out

* docs update

* merge cleanup

* update CI config

* remove rails version warning

* grammar

* remove appraisals for unsupported rails versions

* remove accommodations for Rails < 6.1 in PreviewHelper

* remove support for Rails < 6.1 in Preview layout

* remove old gemfiles

* remove known issue docs for version of rails no longer supported

* remove old rails support in test suite

* simplify render_inline to only support modern Rails

* always include collection_renderer

* remove ruby and rails deprecation warnings in engine.rb

* remove render_monkey_patch

* remove render monkey patch

* update rendering test for rails and ruby deprecations

* remove duplicate components