RFR: 8325495: C2: implement optimization for series of Add of unique value

[Kangcheng Xu]

This pull request resolves [JDK-8325495](https://bugs.openjdk.org/browse/JDK-8325495) by converting series of additions of the same operand into multiplications. I.e., `a + a + ... + a + a + a => n*a`.

As an added benefit, it also converts `C * a + a` into `(C+1) * a` and `a << C + a` into `(2^C + 1) * a` (with respect to constant `C`). This is actually a side effect of IGVN being iterative: at converting the `i`-th addition, the previous `i-1` additions would have already been optimized to multiplication (and thus, further into bit shifts and additions/subtractions if possible).  

Some notable examples of this transformation include:
- `a + a + a` => `a*3` => `(a<<1) + a`
- `a + a + a + a` => `a*4` => `a<<2`
- `a*3 + a` => `a*4` => `a<<2`
- `(a << 1) + a + a` => `a*2 + a + a` => `a*3 + a` => `a*4 => a<<2`

See included IR unit tests for more.

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Commit messages:
 - add more IR tests
 - update comments of existing tests
 - Merge branch 'master' into arithmetic-canonicalization
 - add more IR tests
 - add more IR tests
 - distinguish AndNode from MulNode
 - add initial IR unit tests
 - passes all hotspot-compiler tests
 - implement arithmetic canonicalization for additions

Changes: https://git.openjdk.org/jdk/pull/20754/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20754&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325495
  Stats: 316 lines in 5 files changed: 312 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20754.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20754/head:pull/20754

PR: https://git.openjdk.org/jdk/pull/20754