Fixes gh-12872

Fixes gh-12987

Closes gh-13401

Closes gh-13368

* pr/13344:
  Polish "Fix caching issues with map property sources"
  Fix caching issues with map property sources

Refine the property source cache key fix so that a copy of the
key is only taken when the values change. This allows us to
retain the previous performance optimization of not creating
unnecessary string arrays.

Closes gh-13344

Update `SpringIterableConfigurationPropertySource` so that the cache
key from a `MapPropertySource` is invalidated when the map contents
changes.

Prior to this commit, the actual keys of the map were used as the key.
This meant that if the underlying map changed, they key wouldn't be
invalidated because it ultimately pointed to the same object instance.

See gh-13344

Fixes gh-13399

Prior to this commit, the `DefaultErrorWebExceptionHandler` would parse
the HTTP "Accept" headers when routing the request to the error handler;
if an error occured during parsing, an `InvalidMediaTypeException` would
be thrown and break the error handling for this request.

This commit ignores those exceptions and makes sure that the error
handling function does not override the response status or the error
itself with those exceptions.

Closes: gh-13372

Closes gh-13397

Closes gh-13396

Closes gh-13395

Closes gh-13394

Closes gh-13393

Closes gh-13392

Closes gh-13391

Closes gh-13390

Closes gh-13389

Closes gh-13387

Closes gh-13386

Closes gh-13385

Closes gh-13384

Closes gh-13383

Closes gh-13382

Closes gh-10933

Closes gh-13368

* pr/13378:
  Polish "Replace commons-codec Base64 usage"
  Replace commons-codec Base64 usage

Closes gh-13378

See gh-13378

Update `TomcatResources` so that `META-INF/resources` folders in
`src/main/resources` no longer fail with a "URI is not hierarchical"
exception.

Closes gh-13265

Closes gh-13083

Closes gh-13366

Closes gh-13356