Backport redirects from 7.x.x to 6.x.x
Cherrypicks:
03add9332a06235e39b9b1968f1236a29d87f7cd Rollforward: Restructure rules_java
01c4009 Remove migration tags pollution in the java_* rules
02df6937cda3f627a47d42391b09b7da0fe3b849 Remove Java proto libraries from rules_java
fa37f6120af318849eaf87d1b471e154adf01c61 Rename java/modules to java/common
000ef3c Stop returning legacy struct providers from java_toolchain_alias--
e1d7466 Expose correct symbols from Blaze
ebc35316ef0a0fa7b8a02e3e97ea86d5c1e182b4 Add redirects for proto_registry (ProguardSpecInfo really)
I figured out I can make the latest version backwards compatible, which is even better. https://github.com/bazelbuild/rules_java/pull/210
@comius I presume this is no longer necessary?