RFR: 8284942: Proxy building can just iterate superinterfaces once [v5]

[liach]

> Currently, in ProxyBuilder::mapToModule and ProxyBuilder::defineProxyClass, the interfaces are iterated twice. The two passes can be merged into one, yielding the whole proxy definition context (module, package, whether there's package-private interface) when determining the module.
> 
> Split from #8278. Helpful for moving proxies to hidden classes, but is a good cleanup on its own.

liach has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:

 - Group proxy location validation all into the class context constructor
 - Merge branch 'master' into fix/proxy-single-pass
 - Update
 - Updates suggested by mandy
 - Merge branch 'master' into fix/proxy-single-pass
 - Don't need to complexify module cache
 - 8284942: Proxy building can just iterate superinterfaces once

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8281/files
  - new: https://git.openjdk.java.net/jdk/pull/8281/files/26bde80b..20edc525

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8281&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8281&range=03-04

  Stats: 37340 lines in 627 files changed: 8639 ins; 27112 del; 1589 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8281.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8281/head:pull/8281

PR: https://git.openjdk.java.net/jdk/pull/8281