Closes gh-14950

Update `ApplicationContextAssert.getBean` so that multiple beans are
supported as long as one of them is primary. This aligns better with
the way that the standard `ApplicationContext.getBean` method works.

Closes gh-14874

Fixup sample POM following rename of the oauth2-oidc-client starter.

See gh-14951

Fixup dependencies POM following rename of the oauth2-oidc-client
starter.

See gh-14951

Rename `spring-boot-starter-oauth2-oidc-client` to
`spring-boot-starter-oauth2-client`.

Closes gh-14951

Change `ApplicationConversionService.getSharedInstance()` to again
return a `ConversionService` rather than `ApplicationConversionService`.

This restore binary compatibly with Spring Boot 2.0

Closes gh-14938

Update Thymeleaf and FreeMarker configurations to make use of the new
`@ConditionalOnMissingFilterBean` annotation.

Closes gh-14926

Add a new condition that can be used to check for servlet `Filter`
beans that are either registered directly, or via a
`FilterRegistrationBean`.

Closes gh-14940

Add a `parameterizedContainer` attribute to `ConditionalOnBean` and
`ConditionalOnMissingBean` which can be used to support generic types
when checking for the presence of beans.

Closes gh-14940

Closes gh-14918

* pr/14937:
  Replace lambdas with method reference or call

Closes gh-14937

* gh-14915:
  Polish
  Skip restarter for JUnit5

Closes gh-14915

See gh-14915

Closes gh-14927

See gh-14936

* gh-14910:
  Use Commons Logging for PrometheusPushGatewayManager

Closes gh-14910

* gh-14912:
  Use Errors.hasErrors() in DefaultErrorAttributes

Closes gh-14912

* gh-14916:
  Avoid creation of unnecessary collections

Closes gh-14916

Fix `ResourceUrlEncodingFilter` conditions which were inadvertently
changed in commits 64f04fce and 6cc272ec and would back off if any
`FilterRegistrationBean` was found.

The updated conditions restores the behavior of Spring Boot 2.0.5 and
allows users to directly register their own `ResourceUrlEncodingFilter`
beans (as long as they don't use a `FilterRegistrationBean`).

Fixes gh-14897

This commit also marks a release as pre-release for milestones and RCs

Closes gh-14908
Closes gh-14875

Closes gh-14872