RFR: 8311077: Fix -Wconversion warnings in jvmti code [v2]

[Coleen Phillimore]

> Please review change for mostly fixing return types in the constant pool and metadata to fix -Wconversion warnings in JVMTI code.  The order of preference for changes are: 1. change the types to more distinct types (fields in the constant pool are u2 because that's their size in the classfile), 2. add direct int casts if the value has been checked in asserts above, and 3. checked_cast<> if not verified, and 4. added some pointer_delta_as_ints where needed.
> Tested with tier1-4.

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

  Fred's comments.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14710/files
  - new: https://git.openjdk.org/jdk/pull/14710/files/325cd6e9..c77556da

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14710&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14710&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/14710.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14710/head:pull/14710

PR: https://git.openjdk.org/jdk/pull/14710