RFR: 8331885: C2: meet between unloaded and speculative types is not symmetric [v2]

[Vladimir Ivanov]

> `TypeInstPtr::xmeet_unloaded` computes the MEET of two InstPtrs when at least one is unloaded, but doesn't preserve speculative part if one is present. It causes the corresponding assert to fail. 
> 
> Proposed fix unconditionally keeps speculative part. 
> 
> Testing: hs-tier1 - hs-tier4

Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  AlwaysIncrementalInline is a debugflag

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19249/files
  - new: https://git.openjdk.org/jdk/pull/19249/files/fa5479f2..0b873474

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19249&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19249&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19249.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19249/head:pull/19249

PR: https://git.openjdk.org/jdk/pull/19249