Closes gh-22400

Closes gh-2070

Closes gh-20361

See gh-22341

See gh-22340

Fix for ScriptUtils failure when '--' occurs inside a multi-line comment on the same line as '*/' (#22392)

* Test for multi-line comment block where the comment end delimiter occurs on a line starting with the single-line comment prefix
* ScriptUtils successfully parses a SQL script containing a multi-line comment block where the comment-end delimiter occurs on a line starting with the single-line comment prefix.

Closes gh-22308

* pr/22382:
  Polish contribution
  Polish warning message

Closes gh-22382

See gh-22382

* pr/22373:
  Fix casing for GitHub in the contributing guide

Closes gh-22373

The latter has stale Reactor snapshots

Also removing common PropertyPlaceholderConfigurer doc references.

See gh-22181

Closes gh-22370

Closes gh-22325

Closes gh-22359

Closes gh-22348

See #20945

Fixes gh-22364

Closes gh-22331

See gh-22181

This commit deprecates PropertyPlaceholderConfigurer in favor of
PropertySourcesPlaceholderConfigurer.

Closes gh-22181