Fix the `SystemEnvironmentPropertyMapper.isAncestorOf` implementation
to convert names based on their dashed form and to silently ignore
any invalid results.

Closes gh-14479

Closes gh-21341

Fixes gh-20759

The warnings will be addressed by gh-20759. CreateBootStartScripts
must be excluded from the classes that are validated by the
ValidatePlugins task. It is invalid, but only for Gradle 6.4. gh-20759
will cause it to only be used with Gradle 6.3 and earlier.

See gh-21329

Closes gh-21340

Closes gh-21339

Closes gh-21338

Closes gh-21337

Closes gh-21336

Closes gh-21335

Closes gh-21334

Closes gh-21333

Closes gh-21332

Closes gh-21331

Closes gh-21330

Closes gh-21329

Closes gh-21327

Previously, unlike embedded Jetty, Netty, and Tomcat, Undertow would
not stop when one of its worker threads was in use. This meant that a
a long-running or stalled request could prevent the application from
shutting down in response to SIGTERM or SIGINT, and SIGTERM would be
required to get the process to exit.

This commit updates the factories for the reactive and servlet
Undertow web server factories to configure Undertow to use a 0ms
shutdown timeout. This aligns it with the behaviour of Jetty, Netty,
and Tomcat. Tests have been introduced to verify the behaviour across
the reactive and servlet variants of all four supported embedded web
servers.

Fixes gh-21319

Fixes gh-21288

* pr/21136:
  Polish 'Add Period converter support'
  Add Period converter support

Closes gh-21136

Polish period converter support, primarily by changing
`PeriodStyle` to parse and print periods that include
more than one unit.

See gh-21136

Add converter support for `javax.time.Period` including:

	String -> Period
	Number -> Period
	Period -> String

Period to Number conversion is not supported since `Period` has no
ability to deduce the number of calendar days in the period.

See gh-21136

Update the `isAncestorOf` method of SpringConfigurationPropertySources
so that legacy names are considered for the system environment.

Prior to this commit, binding a property such as `my.camelCase.prop`
would detect `MY_CAMELCASE_PROP` but not `MY_CAMEL_CASE_PROP` in
the system environment.

Fixes gh-14479
Co-authored-by: Phillip Webb <pwebb@pivotal.io>

* pr/21259:
  Further optimize StringSequence.startsWith
  Optimize StringSequence.startsWith

Closes gh-21259

See gh-21259

See gh-21259

Closes gh-21292

Closes gh-21323

Fixes gh-17001

Upgrade JNA to 5.5.0 and only use the jna-platform dependency.

Closes gh-21313

Closes gh-21321

Closes gh-21320

Update `StaticResourceJars` to catch both `IOException` and
`InvalidPathException` when checking URLs. Prior to this commit only
`IOException` was caught which worked on Java 8 but not Java 11 or
above.

Fixes gh-21312

Extend wildcard restrictions to the `spring.config.name` property. Also
refine exception messages to include the property value.

Closes gh-21217

* pr/21108:
  Fix duplicate slashes in URL links

Closes gh-21108

See gh-21108

Closes gh-21315

Closes gh-21314