JDK HTTP Client: Support Brotli compression

[kwin]

New feature, improvement proposal

Maven Central is supposed to support Brotli compression soon. It already works on https://repo1.maven.org/maven2/archetype-catalog.xml. In order to benefit from compression also within Maven the JDK Transport should support it for all text-based files (like XML).

[kwin]

@cstamas Is it fine to rely on https://github.com/jetty/jetty.project/releases/tag/jetty-12.1.0 for testing, as only that introduced compression support? That means that those Tests can only be executed with Java 17+.

[cstamas]

Yup, is fine IMO. Build requires Java 21 anyway (but produces Java 8 bytecode JARs; most of them).