RFR: 8290833: Remove ConstantPoolCache::walk_entries_for_initialization() [v4]

[Ioi Lam]

> **Background:**
> 
> `ConstantPoolCache::walk_entries_for_initialization()` is called by `ConstantPoolCache::remove_unshareable_info()` to restore the CpCache to the state immediately after the class has been rewritten by the Rewriter (which happens during the class linking phase). In most part, this means the `ConstantPoolCacheEntry`'s need to be zeroed. However, the `_f2` fields of some of the entries are initialized to be non-zero by the Rewriter and must be preserved.
> 
> The reason `walk_entries_for_initialization()` exists is that after `Rewriter::rewrite()` has finished, some information about what is stored inside the CpCache is discarded (e.g., `Rewriter::_invokedynamic_references_map`). As a result, we cannot easily determine which entries has a `_f2` field that need to be preserved. We must walk all the bytecodes in all the methods of this class to recompute this information.
> 
> This is awkward and time consuming. It also needs to be updated if the `Rewriter` ever changes.
> 
> Also, for future optimizations, we may need to pre-resolve a subset of the CpCache entries during CDS dump time. Trying to make that work alongside `walk_entries_for_initialization()` seems too complicated.
> 
> **Fix:**
> 
> Store a copy of the CpCache after rewritting. Use this to revert the CpCache's state inside  `ConstantPoolCache::remove_unshareable_info()`.

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  @coleenp review comments; added asserts

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9759/files
  - new: https://git.openjdk.org/jdk/pull/9759/files/dcf1c54c..eb99170b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9759&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9759&range=02-03

  Stats: 7 lines in 3 files changed: 4 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/9759.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9759/head:pull/9759

PR: https://git.openjdk.org/jdk/pull/9759