Add a new `ClientHttpRequestFactoryBuilder` interface to support the
creation of `ClientHttpRequestFactory` instances. The new code will
ultimately replace the existing `ClientHttpRequestFactories` class.
The `ClientHttpRequestFactoryBuilder` is a functional interface with
additional static factory methods for the various supported
`ClientHttpRequestFactory` types. Each type has it's own builder
which should allow us to support additional customization in the future.
Unlike `ClientHttpRequestFactories`, the builder aligns with Spring
Framework defaults and will detect the `JdkClientHttpRequestFactory`
in preference of `SimpleClientHttpRequestFactory`.
This commit also relocates `ClientHttpRequestFactorySettings` to bring
it into the new `http.client` package.
See gh-36266
78458afa17