RFR: 8284942: Proxy building can just iterate superinterfaces once [v2]

[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 incrementally with one additional commit since the last revision:

  Don't need to complexify module cache

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8281/files
  - new: https://git.openjdk.java.net/jdk/pull/8281/files/08796879..d58bb7e0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8281&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8281&range=00-01

  Stats: 8 lines in 1 file changed: 0 ins; 2 del; 6 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