[lworld] RFR: 8378105: [lworld] [REDO] Follow up 8329433 for Valhalla entry points in nmethod

[Manuel Hässig]

This is a redo of #2116.

This PR makes the necessary changes to also make the inline entry point fields in the nmethod class a `uint16_t` like JDK-8329433 did for the other entry points. Importantly, this PR preserves the default values necessary for unused entry points.

Testing:
- [ ] tier1,tier2,tier3

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Commit messages:
 - [REDO] Make valhalla entry points uint16_t

Changes: https://git.openjdk.org/valhalla/pull/2123/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2123&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378105
  Stats: 34 lines in 4 files changed: 7 ins; 1 del; 26 mod
  Patch: https://git.openjdk.org/valhalla/pull/2123.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2123/head:pull/2123

PR: https://git.openjdk.org/valhalla/pull/2123