[lworld] RFR: 8351006: [lworld] Refactor LoadNode::Identity of an InlineType into can_see_stored_value

[Quan Anh Mai]

Hi,

This patch moves the logic of `LoadNode::Identity` that tries to look through an `InlineTypeNode` to `can_see_stored_value`. This also fixes 2 issues:

- `Identity` should not return a new node
- `LoadUS` from a `short` is not a mismatched access and hence can return a wrong value

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

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Commit messages:
 - Refactor LoadNode::Identity of an InlineTypeNode to can_see_stored_value

Changes: https://git.openjdk.org/valhalla/pull/1387/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1387&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351006
  Stats: 50 lines in 2 files changed: 33 ins; 17 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1387.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1387/head:pull/1387

PR: https://git.openjdk.org/valhalla/pull/1387