RFR: 8284942: Proxy building can just iterate superinterfaces once [v4]

[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:

  Update

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8281/files
  - new: https://git.openjdk.java.net/jdk/pull/8281/files/502dad82..26bde80b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8281&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8281&range=02-03

  Stats: 8 lines in 1 file changed: 5 ins; 0 del; 3 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