RFR: 8260337: Optimize ImageReader lookup, used by Class.getResource [v2]

[Claes Redestad]

> This patch optimizes the code paths exercised by `String.class.getResource("String.class")` by:
> 
> - Adding an ASCII fast-path to methods verifying strings in the jimage, which can then be done allocation-free
> - Avoiding the allocation of the `long[8]` attributes when verifying only for the purpose of verifying a path exists
> - Using the `JNUA.create` fast-path in `SystemModuleReader` (which should be OK since we just verified the given name is a JRT path)
> - Remove a redundant check in `Class::resolveName` and fitting the `StringBuilder` to size

Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:

  Copyrights and rename containsLocation

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2212/files
  - new: https://git.openjdk.java.net/jdk/pull/2212/files/ad95b490..096e64b1

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2212&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2212&range=00-01

  Stats: 10 lines in 7 files changed: 0 ins; 0 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2212.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2212/head:pull/2212

PR: https://git.openjdk.java.net/jdk/pull/2212