RFR: 8313785: Fix -Wconversion warnings in prims code [v2]

[Coleen Phillimore]

> This patch fixes Wconversion in code in the src/hotspot/share/prims directory.  Most of the changes correct the types.  jfieldID's are created with the int offset returned by InstanceKlass::field_offset().
>      int     field_offset      (int index) const { return field(index).offset(); }
> 
> So when we get the field offset back, it's an int.
> 
> Also stackwalker passes jlong, so made that consistent.
> 
> Tested with tier1 on Oracle supported platforms.

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

  Dean's suggested changes.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/15160/files
  - new: https://git.openjdk.org/jdk/pull/15160/files/a693cc38..07304dd2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15160&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15160&range=00-01

  Stats: 6 lines in 2 files changed: 0 ins; 3 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/15160.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15160/head:pull/15160

PR: https://git.openjdk.org/jdk/pull/15160