RFR: 8257630: ReplacedNodes doesn't handle non-CFG multi nodes

[Vladimir Ivanov]

When looking up an immediate CFG node, ReplacedNodes assumes that control input is always a CFG node. 
It's not always the case: for example, a projection on a non-CFG multi node (`SCMemProj` and `LoadStore` respectively).

Proposed fix is to skip projection nodes first before checking for CFG.

Testing:
- [x] hs-tier1-6 w/ -XX:+AlwaysIncrementalInlining

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Commit messages:
 - ReplacedNodes doesn't handle non-CFG multi nodes well

Changes: https://git.openjdk.java.net/jdk/pull/1580/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1580&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257630
  Stats: 8 lines in 1 file changed: 3 ins; 1 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1580.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1580/head:pull/1580

PR: https://git.openjdk.java.net/jdk/pull/1580