RFR: 8325871: Move StringTable and SymbolTable rehashing calls [v2]

[Coleen Phillimore]

> Move the rehashing calls as a test in the concurrent work - ie. trigger concurrent work and check for the need to do rehashing. 
> 
> Tested with tier1-7.

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

  In CHT copy_nodes_to is really rehash_nodes_to, so rename it less generically.  This function can never fail now that rehashing is done in a dedicatd safepoint for that purpose, so resizing will never be concurrent.  do_hash moved into rehash_table.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18240/files
  - new: https://git.openjdk.org/jdk/pull/18240/files/b22e8db7..24d3f35e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18240&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18240&range=00-01

  Stats: 93 lines in 7 files changed: 20 ins; 46 del; 27 mod
  Patch: https://git.openjdk.org/jdk/pull/18240.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18240/head:pull/18240

PR: https://git.openjdk.org/jdk/pull/18240