RFR: 8253734: C2: Optimize Move nodes

[Vladimir Ivanov]

Introduce the following transformations for Move nodes: 
1. `MoveI2F (MoveF2I x) => x`

1. `MoveI2F (LoadI mem) => LoadF mem` 

1. `StoreI mem (MoveF2I x) => StoreF mem x` 

(The same applies to MoveL2D/MoveD2L.)

№1 eliminates redundant operations and №2/№3 avoid reg-to-reg moves in generated code:
0x000000010d09964c:   vmovss 0x20(%rsi),%xmm1
0x000000010d099651:   vmovd  %xmm1,%eax                   ;*invokestatic floatToRawIntBits
vs
0x0000000110c5a6cc:   mov    0x20(%rsi),%eax              ;*invokestatic floatToRawIntBits
 

(№2 and №3 are performed late (after loop opts are over) to avoid high-level optimizations passes to handle newly introduced mismatched accesses.)

Testing: tier1-5.

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Commit messages:
 - 8253734: Optimize Move nodes

Changes: https://git.openjdk.java.net/jdk/pull/826/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=826&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253734
  Stats: 142 lines in 5 files changed: 127 ins; 0 del; 15 mod
  Patch: https://git.openjdk.java.net/jdk/pull/826.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/826/head:pull/826

PR: https://git.openjdk.java.net/jdk/pull/826