Remove scheduled deprecations

Remove the following scheduled (and announced) deprecations from the code:

• ensureGitSuffix key from git category in playbook file (it should be written as ensure_git_suffix)
• pull key from runtime category in playbook (it should be written as fetch)
• getFiles method on content catalog and site catalog (it should be written as getAll)
• getComponentMap method on content catalog (site.components in UI model is already a map)
• getComponentMapSortedBy method on content catalog (was previously not used; use getComponentsSortedBy instead)
• latestVersion property on component version object (it should be written as latest)
• remove fallback call to resolve asciidocConfig in classifyContent function (it must be passed in as third parameter site generator)
• rename exported resolveConfig function in AsciiDoc loader to resolveAsciiDocConfig (keep resolveConfig function as alias for backwards compatibility in Antora 3)
• don't automatically append .adoc to page ID on xref or start page (the .adoc must be present to refer to a page)
  • we will continue to honor this shorthand for page aliases until at least the next major to give more time to migrate
• treat all non-URI image targets as resource IDs (which will disallow parent references in target of image macro)
• remove intrinsic page-relative attribute (replaced by page-relative-src-path)

An open question is whether we should remove support for the pages/_partials location for storing partials, or whether we should only start warning about it and remove support for it in a future major.