Closes gh-19772

The release didn't happen in time for 2.2.3.

See gh-19645

The release did not happen in time for 2.1.12.

See gh-19649.

Update the Maven plugin with a new `LAYERED_JAR` layout option.

See gh-19768

Support an alternative fat jar format that is more amenable to Docker
image layers.

The new format arranges files in the following structure:

	BOOT-INF/
	  layers/
	    <layer-name #1>
	      /classes
	      /lib
	    <layer-name #2>
	      /classes
	      /lib

The `BOOT-INF/layers.idx` file provides the names of the layers and the
order in which they should be added (starting with the least changed).

The `JarLauncher` class can load layered jars in both fat and exploded
forms.

Closes gh-19767
Co-authored-by: Phillip Webb <pwebb@pivotal.io>

Update the `Repackager` class so that an additional `classpath.idx` file
is written into the jar that provides the original order of the
classpath. The `JarLauncher` class now uses this file when running as
an exploded archive to ensure that the classpath order is the same as
when running from the far jar.

Closes gh-9128
Co-authored-by: Phillip Webb <pwebb@pivotal.io>

Polish and refactor `spring-boot-loader` and `spring-boot-loader-tools`
to make it easier to add indexing and layering support.

Closes gh-19766

The JarFile was not being closed which linked a file handle and caused
a test failure on Windows.

The local variable has been renamed as, when declared in a
try-with-resources, Checkstyle was confused by the shadowing of the
jarFile field and required references to jarFile within the try-block
the be prefixed with this.

See gh-19595

Closes gh-19613

Closes gh-19647

Closes gh-19646

publishIfAuthenticated() does not appear to work as intended as it
disables publishing even when authenticated.

Closes gh-19761

Closes gh-19641

Closes gh-19648

Closes gh-19644

Closes gh-19758

Closes gh-19757

Closes gh-19756

Closes gh-19755

Closes gh-19754

Closes gh-19753

Closes gh-19752

Closes gh-19751

Closes gh-19750

Closes gh-19749

Closes gh-19748

Closes gh-19747

Closes gh-19746

Closes gh-19745