Closes gh-24048

Closes gh-24048

Also restores immediate MethodOverrides instance in AbstractBeanDefinition, avoiding potential lazy-init race condition.

Closes gh-23448

This covers ApplicationListener generics in factory method return types in particular but also allows for programmatic setTargetType hints.

Closes gh-23178

Closes gh-23093

Closes gh-22960

Closes gh-22694

This commit updates URLs to prefer the https protocol. Redirects are not followed to avoid accidentally expanding intentionally shortened URLs (i.e. if using a URL shortener).

# Fixed URLs

## Fixed Success
These URLs were switched to an https URL with a 2xx status. While the status was successful, your review is still recommended.

* [ ] http://www.apache.org/licenses/ with 1 occurrences migrated to:
  https://www.apache.org/licenses/ ([https](https://www.apache.org/licenses/) result 200).
* [ ] http://www.apache.org/licenses/LICENSE-2.0 with 6515 occurrences migrated to:
  https://www.apache.org/licenses/LICENSE-2.0 ([https](https://www.apache.org/licenses/LICENSE-2.0) result 200).

This commit updates URLs to prefer the https protocol. Redirects are not followed to avoid accidentally expanding intentionally shortened URLs (i.e. if using a URL shortener).

# Fixed URLs

## Fixed Success
These URLs were switched to an https URL with a 2xx status. While the status was successful, your review is still recommended.

* [ ] http://www.apache.org/licenses/ with 1 occurrences migrated to:
  https://www.apache.org/licenses/ ([https](https://www.apache.org/licenses/) result 200).
* [ ] http://www.apache.org/licenses/LICENSE-2.0 with 6625 occurrences migrated to:
  https://www.apache.org/licenses/LICENSE-2.0 ([https](https://www.apache.org/licenses/LICENSE-2.0) result 200).

Also includes setters for role and description.

Issue: SPR-17275

Empty Maps are preferably initialized without capacity (not initializing them at all or lazily initializing with default capacity when needed).

Issue: SPR-17105

Ensure that `this.` is used consistently when accessing class
fields.

Issue: SPR-16968

Update all code to use a consistent block style.

Issue: SPR-16968

Issue: SPR-16192

Issue: SPR-15532

Issue: SPR-15869

This commits extends nullability declarations to the field level, formalizing the interaction between methods and their underlying fields and therefore avoiding any nullability mismatch.

Issue: SPR-15720

Beyond just formally declaring the current behavior, this revision actually enforces non-null behavior in selected signatures now, not tolerating null values anymore when not explicitly documented. It also changes some utility methods with historic null-in/null-out tolerance towards enforced non-null return values, making them a proper citizen in non-null assignments.

Some issues are left as to-do: in particular a thorough revision of spring-test, and a few tests with unclear failures (ignored as "TODO: NULLABLE") to be sorted out in a follow-up commit.

Issue: SPR-15540

This commit introduces 2 new @Nullable and @NonNullApi
annotations that leverage JSR 305 (dormant but available via
Findbugs jsr305 dependency and already used by libraries
like OkHttp) meta-annotations to specify explicitly
null-safety of Spring Framework parameters and return values.

In order to avoid adding too much annotations, the
default is set at package level with @NonNullApi and
@Nullable annotations are added when needed at parameter or
return value level. These annotations are intended to be used
on Spring Framework itself but also by other Spring projects.

@Nullable annotations have been introduced based on Javadoc
and search of patterns like "return null;". It is expected that
nullability of Spring Framework API will be polished with
complementary commits.

In practice, this will make the whole Spring Framework API
null-safe for Kotlin projects (when KT-10942 will be fixed)
since Kotlin will be able to leverage these annotations to
know if a parameter or a return value is nullable or not. But
this is also useful for Java developers as well since IntelliJ
IDEA, for example, also understands these annotations to
generate warnings when unsafe nullable usages are detected.

Issue: SPR-15540

Issue: SPR-15072

Issue: SPR-14832

Issue: SPR-13188

Issue: SPR-13188

Issue: SPR-14333

Previously, a Bean implementing `AutoCloseable` (or `Closeable`) was
always destroyed regardless of its bean definition. In particular, the
documented way of disabling the destruction callback via an empty String
did not work.

AutoCloseable beans are now treated pretty much as any other bean: we
still use the presence of the interface to optimize the check of a
destroy method and we only auto-discover the method name to invoke if
the inferred mode is enabled.

Issue: SPR-13022

(cherry picked from commit a1396702)

Issue: SPR-11680

Issue: SPR-11422

Fix remaining Java compiler warnings, mainly around missing
generics or deprecated code.

Also add the `-Werror` compiler option to ensure that any future
warnings will fail the build.

Issue: SPR-11064

Issue: SPR-10130