Remove deprecated SSL settings from Elasticsearch input plugin

[robbavey]

• Create branch from most recent commit on main
• All plugin changes that remove SSL settings should be in a new major release of the plugin Remove deprecated SSL settings and simplify SSL configuration #213
• Mark old SSL settings as obsolete
• Add breaking change entry to plugin changelog
• Add details of change to the 9.0 breaking changes documentation in core.
  - [] Verify that any integration tests in core that rely on SSL settings still work. Fix any broken integration tests
• Verify plugin documentation, remove any references to deprecated settings

[donoghuc]

NOTE: No integration tests in core explicitly configure this plugin.