RFR: 8263591: Two C2 compiler phases with the name "after matching"

[Tobias Hartmann]

[JDK-8223347](https://bugs.openjdk.java.net/browse/JDK-8223347) added a `PHASE_AFTER_MATCHING` which is equivalent to  `PHASE_MATCHING` but only printed at level 3 and before node verification: 
https://github.com/openjdk/jdk/blob/20297a1bebfe03c45344a713ec561c97888c4750/src/hotspot/share/opto/compile.cpp#L2757-L2769

I don't think there is any benefit in having both and therefore removed it together with some other dead code (`idx` is always `0`).

Thanks,
Tobias

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Commit messages:
 - 8263591: Two C2 compiler phases with the name "after matching"

Changes: https://git.openjdk.java.net/jdk/pull/3026/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3026&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263591
  Stats: 12 lines in 2 files changed: 0 ins; 5 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3026.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3026/head:pull/3026

PR: https://git.openjdk.java.net/jdk/pull/3026