2.6 changelog gen/version/root dir cleanup (#40421)

* patched in changelog gen stuff from stable-2.5
* Makefile updates
* release.py as single-source-of-truth
* Remove obsolete ansible-core-sitemap.xml file.
* Move ROADMAP.rst into README.rst.
* dynamic rpm changelog, zap old deb/rpm changelogs
* fix changelog in MANIFEST.in
* Remove obsolete hacking/update.sh script.
* Remove ref to deleted authors script.
* Remove ref to removed module-formatter script.
* Update headings to match script names.
* MANIFEST.in cleanup
* removed RELEASES.txt and versions.yml
* removed obsolete release generation playbook/bits (not used since 2.5)
* misc Makefile cleanup
* speculative changes to DEB versioning
* allow override of DEB_VERSION/DEB_RELEASE

changelogs/config.yaml

@@ -0,0 +1,18 @@
+---
+release_tag_re: '(v(?:[\d.ab\-]|rc)+)'
+pre_release_tag_re: '(?P<pre_release>(?:[ab]|rc)+\d*)$'
+notesdir: fragments
+prelude_section_name: release_summary
+sections:
+- ['major_changes', 'Major Changes']
+- ['minor_changes', 'Minor Changes']
+- ['deprecated_features', 'Deprecated Features']
+- ['removed_features', 'Removed Features (previously deprecated)']
+- ['new_lookup_plugins', 'New Lookup Plugins']
+- ['new_callback_plugins', 'New Callback Plugins']
+- ['new_connection_plugins', 'New Connection Plugins']
+- ['new_test_plugins', 'New Test Plugins']
+- ['new_filter_plugins', 'New Filter Plugins']
+- ['new_modules', 'New Modules']
+- ['bugfixes', 'Bugfixes']
+- ['known_issues', 'Known Issues']

changelogs/fragments/v2.6.0a1_catchup.yaml

@@ -0,0 +1 @@
+{}