RFR: 8292318: Memory corruption in remove_dumptime_info [v2]

[Ioi Lam]

> In [JDK-8290833](https://bugs.openjdk.org/browse/JDK-8290833) (#9759), I added a table (`SystemDictionaryShared::_saved_cpcache_entries_table`) that remembers the initial state of a `ConstantPoolCache` during CDS dumping. This table is indexed with a `ConstantPoolCache*`
> 
> However, `ConstantPoolCache` has a complex lifecycle, especially with class redefinition. This makes it difficult to clean up the table. The crash reported in [the current bug](https://bugs.openjdk.org/browse/JDK-8292318) happened during clean up, probably because an `InstanceKlass` was still valid but its `ConstantPool` or `ConstantPoolCache` were not.
> 
> For simplification, I am now storing the information inside the `ConstantPoolCache`. To compensate for the extra space used, I moved two 32-bit integers next to each other, so the net change in size is zero.
> 
> instanceKlass.cpp was reverted to the state before #9759.

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

  added comments about what _initial_entries points to

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9887/files
  - new: https://git.openjdk.org/jdk/pull/9887/files/7d38f55f..a2872fae

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9887&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9887&range=00-01

  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9887.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9887/head:pull/9887

PR: https://git.openjdk.org/jdk/pull/9887