RFR: 8374308: ImageBufferCache does not work as intended [v4]

[David Beaumont]

> Remove ineffective/unused ImageBufferCache class, and simplify callers / remove dead code.
> 
> I removed the release methods in the internal classes, but the public ModuleReader API method is still there (the override can go away though since the default implementation also tests for non-null, so removing the override has no risk).
> 
> I suspect there are no implementations of ModuleReader that implement release semantics after this change, so perhaps we could relax the documentation around it? Thoughts welcome.

David Beaumont has updated the pull request incrementally with one additional commit since the last revision:

  simplifying allocation and argument checks

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29043/files
  - new: https://git.openjdk.org/jdk/pull/29043/files/e3bbc4c5..7d54c8e5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29043&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29043&range=02-03

  Stats: 18 lines in 1 file changed: 2 ins; 10 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/29043.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29043/head:pull/29043

PR: https://git.openjdk.org/jdk/pull/29043