RFR: 8264997: Remove SystemDictionary::cache_get [v2]

[Coleen Phillimore]

> This is a trivial change to remove an unneeded function in SystemDictionary.  The pd_cache_table() that is owned by SystemDictionary is already available to callers of SystemDictionary, ie. the ServiceThread, so there's no need to hide access inside of a function with a backwards name.
> 
> I also fixed add_protection_domain logging to be useful and fixed an assert.
> 
> Tested with mach5 tier1-3 in progress and manually.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Missed fixing logging test.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3418/files
  - new: https://git.openjdk.java.net/jdk/pull/3418/files/9a661354..7900de31

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3418&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3418&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3418.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3418/head:pull/3418

PR: https://git.openjdk.java.net/jdk/pull/3418