[lworld] RFR: 8378672: [lworld] Consolidate a factory to create a GraphKit from a SafePointNode

[Quan Anh Mai]

Hi,

I find it is a common occurrence that we want to expand a `SafePointNode` into a subgraph, and to do that we may need to create a `JVMState` ourselves, which may easily results in cumbersome errors because the kit state is not created properly. I tried using `GraphKit` to expand generate code after a `SafePointNode` (in particular, I tried to emit an uncommon trap there), which leads to this PR which consolidates the creation of a `GraphKit` from a `SafePointNode` that we want to use its debug state.

Please take a look and leave your reviews, thanks a lot.

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Commit messages:
 - GraphKit for macro expansion

Changes: https://git.openjdk.org/valhalla/pull/2163/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2163&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378672
  Stats: 42 lines in 3 files changed: 26 ins; 10 del; 6 mod
  Patch: https://git.openjdk.org/valhalla/pull/2163.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2163/head:pull/2163

PR: https://git.openjdk.org/valhalla/pull/2163