RFR: 8329469: Generational ZGC: Move the methods forwarding_[index|find|insert] from zRelocate.cpp to ZForwarding [v3]

[Guoxiong Li]

> Hi all,
> 
> This patch moves the methods `zRelocate.cpp/forwarding_[index|find|insert]`  from the file `zRelocate.cpp` to the class `ZForwarding`.  The first parameter of the methods `zRelocate.cpp/forwarding_[index|find|insert]` is always `ZForwarding*`. These methods should be placed in the class `ZForwarding` so that the first parameter `ZForwarding*` can be added by the compiler and then it can improve the encapsulation.
> 
> But the non-generational ZGC can't make such a move because the method signatures may be duplicate.
> 
> The test `make test-tier1_gc` passed locally. Thanks for taking the time to review.
> 
> Best Regards,
> -- Guoxiong

Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:

  Add blank lines.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18579/files
  - new: https://git.openjdk.org/jdk/pull/18579/files/e41b93bc..fb077d76

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18579&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18579&range=01-02

  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18579.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18579/head:pull/18579

PR: https://git.openjdk.org/jdk/pull/18579