DP-46939: Clean up / modernize mass_caching

[tfleming-ma]

Description:
Follow-up to #3366

Changes

• Moved all hook implementations to classes in src/Hook to take advantage of new Hook system
• Added unit tests for new Hook implementations
• Set mass_caching.skip_procedural_hook_scan to true in mass_caching.services.yml. See https://www.drupal.org/node/3490771
• Created new drush command for DeployCommands to run instead of the drush command that evaluated the ManualPurger service directly
• Updated how the ManualPurger service is defined
• Fixed deprecated method calls and removed workarounds for fixed bugs (PathAliasPurgeHooks, PurgerHooks)
• Removed Cloudflare purger and maintenance mode check, which was only used by the Cloudflare purger

Jira: (Skip unless you are MA staff)
DP-46939

To Test:

• Check ExistingSite and Unit tests
• Run new manual purger command, preferably close to how used in DeployCommands
• On feature environment, test saving pages and check purge queue

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Peer Review Checklist