Update to Rails 8.1, Ruby 3.4

[awilfox]

• Gem updates for Rails 8.1 compatibility and latest security fixes.

• Load the 8.1 config defaults.

• Update config files with new 8.1 configuration.

• Ensure Docker library doesn't crash inside Podman.

• Minor style fixes for Rubocop.

Closes: AP-758

[awilfox]

v2:

• Update SimpleCov to 1.0.0.rc4; it gets confused otherwise.
• Update .simplecov file to new standards to avoid deprecation warnings.

[awilfox]

Cool. CI failure:

Offenses:

spec/support/matchers/hash_diff_matcher.rb:94:7: W: [Correctable] Lint/RedundantCopDisableDirective: Unnecessary disabling of Metrics/MethodLength.
      # rubocop:disable Metrics/MethodLength
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

107 files inspected, 1 offense detected, 1 offense autocorrectable

yet if I do that, then locally I get:

Offenses:

spec/support/matchers/hash_diff_matcher.rb:94:7: C: Metrics/MethodLength: Method has too many lines. [12/10]
      def formatted_diffs ...
      ^^^^^^^^^^^^^^^^^^^

107 files inspected, 1 offense detected

will try breaking my local build and seeing if that fixes CI…

[awilfox]

v3:

• Yes, breaking my local build makes CI pass. lovely!

[anarchivist]

r+. thanks!