RFR: 8271073: Improve testing with VM option VerifyArchivedFields [v2]

[Ioi Lam]

> - Changed the definition of `VerifyArchivedFields` from a whacky use of `bool` to an `int` and properly define its three levels:
>   - 0: No verification 
>   - 1: Basic verification with VM_Verify (no side effects)
>   - 2: Detailed verification by forcing a GC (with side effects)
> - Changed the default value to 0. The functionality checked by this flag has been very stable so there's no need to verify it in every single test case.
> - Enabled `-XX:VerifyArchivedFields=1` for all CDS test cases.
> - Added a new test case for `-XX:VerifyArchivedFields=2` .
> - Also added comments about that this flag is suppose to check for.

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

  the test should require vm.cds.write.archived.java.heap

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5514/files
  - new: https://git.openjdk.java.net/jdk/pull/5514/files/b8e22df2..d7cd3a5b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5514&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5514&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5514.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5514/head:pull/5514

PR: https://git.openjdk.java.net/jdk/pull/5514