RFR: 8253303 G1: Move static initialization of G1FromCardCache to a proper location

[Thomas Schatzl]

in src/hotspot/share/gc/g1/g1RemSet.cpp:

 488 void G1RemSet::initialize(uint max_reserved_regions) {
 489 G1FromCardCache::initialize(num_par_rem_sets(), max_reserved_regions);
 490 _scan_state->initialize(max_reserved_regions);
 491 }

the static initialization is piggy-backed to G1RemSet instance initialization which is rather bad style. Fortunately
there is only one G1RemSet instance and that method is only called once so no functional issue.

This change moves the initialization call, and after a bit of analysis move some more related code to more appropriate
places.

Testing: local compilation, jtreg gc/g1, tier1-3 running

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Commit messages:
 - Initial revision

Changes: https://git.openjdk.java.net/jdk/pull/247/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=247&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253303
  Stats: 36 lines in 5 files changed: 17 ins; 12 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/247.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/247/head:pull/247

PR: https://git.openjdk.java.net/jdk/pull/247