Fixes gh-13535

* gh-12859:
  Polish "Fix JSP availability check when not running as a packaged war"
  Fix JSP availability check when not running as a packaged war

Closes gh-12859

See gh-12859

Previously, if an HTTP request that used a templated URI was handled
by something other than Spring MVC, a potentially unbounded number of
metrics would be created. This happened because, in the absence of
Spring MVC's best matching pattern attribute, MetricsFilter would fall
back to using the request's path. If the handling route was templated,
MetricsFilter would be unaware and would record different metrics for
each different path, rather than a single metric for the matching
pattern.

This cimmit updates MetricsFilter so that it falls back to using
unmapped when Spring MVC's best matching pattern attribute is not
available. This ensures that an unbounded number of metrics will no
longer be created, at the cost of losing specific metrics for requests
that are not handled by Spring MVC and that do not use a templated
path.

Closes gh-5875

Closes gh-13493

Closes gh-13538

This starter does not look maintained anymore and there is an
alternative that we also reference and has support for Spring Boot 2.

This starter does not look maintained anymore and there is a fork of it
that we also reference and has support for Spring Boot 2.

Closes gh-12729

Log4J2 enables its shutdown hook by default. When the JVM is exiting,
this creates a race between logging that happens during the
application context being closed and Log4J2 being shut down such that
the logging is lost.

This commit updates SpringBootConfigurationFactory so that it
produces a custom sub-class of DefaultConfiguration that disables the
shutdown hook by default. In addition to solving the problem described
above, this also aligns the Log4J2 logging system with the
logging.register-shutdown-hook property which defaults to false.

Closes gh-11360

Closes gh-13534

* pr/13534:
  Polish

See gh-13534

See gh-13534

Closes gh-12742