Closes gh-12739

Closes gh-12344

Closes gh-12748

Closes gh-12734

Closes gh-12736

Closes gh-12735

* gh-12715:
  Polish "Use modifiable set for @ServletComponentScan with no packages"
  Use modifiable set for @ServletComponentScan with no packages

Closes gh-12715

Previously, when a project contained multiple `@ServletComponentScan`
annotated classes in classpath, and at least one annotation don't
explicitly specify `basePackages` and `basePackageClass` attribute,
the application could fail to start with an
UnsupportedOperationException. The failure occurred due to the
creating of an unmodifiable set when no base packages are configured
and a subsequent attempt to add base packages to that sit.

This commit fixes the issue by removing the use of an unmodifiable set
when `@ServletComponentScan` with no base packages in processed before
any other `@ServletComponentScan` annotations.

See gh-12715

Closes gh-12731

Closes gh-12730

Update `Restarter` to be much more defensive when attempting to clear
caches. We now use `clearCache()` methods whenever possible, and only
fall back to field access when absolutely necessary. In addition field
access now ignore any exceptions.

Fixes gh-12719

See gh-12695

See gh-12692

Closes gh-12526

* pr/12629:
  Polish "Use secure connection to repositories"
  Use secure connection to repositories

Closes gh-12629

See gh-12629

Closes gh-12636

* pr/12535:
  Fix ModifiedClassPathRunner tests if run via IDEA

IntelliJ can shorten the classpath to a single classpath.jar in order to
circumvent errors originating from a too long classpath. This breaks the
filtering inside ModifiedClassPathRunner as the classpath contains only a
single jar to match against. This can be fixed by applying a similar
mechanism already provided for Surefire manifest-only booter JARs, which
extracts the real classpath from the JAR's Manifest file.

See gh-12535

Closes gh-12614

Closes gh-12613

Closes gh-12573

* gh-12554:
  Polish "Use this.out in SummaryProgressReporter.finished()"
  Use this.out in SummaryProgressReporter.finished()

See gh-12554

Closes gh-12554

Refine `BasicErrorController` mappings so that only JSON and XML get
structured responses. A simple string response is returned for all
other media types.

Fixes gh-12513

Update JAR `Handler` logic so that the existing `jarFile` is only used
if the requested URL starts with the same path. Prior to this commit it
was possible to construct a URL with another URL as context. This could
mean that the `handler` was shared and the already resolved `jarFile`
contained in the handler wasn't necessarily suitable.

Fixes gh-12483

Closes gh-12393

Closes gh-12498

Closes gh-12497

Closes gh-12496

* pr/12422:
  Polish

Closes gh-12422

Closes gh-12434

Closes gh-12409