RFR: 8325495: C2: implement optimization for series of Add of unique value [v2]

[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.

Kangcheng Xu has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 22 additional commits since the last revision:

 - Merge branch 'openjdk:master' into arithmetic-canonicalization
 - Merge pull request #1 from tabjy/arithmetic-canonicalization-v2
   
   Arithmetic canonicalization v2
 - remove dead code
 - fix potential void type const nodes
 - refactor and cleanup
 - add more test cases
 - re-implement depth limit on recursion
 - passes TestIRLShiftIdeal_XPlusX_LShiftC
 - passes AddI[L]NodeIdealizationTests
 - revert depth limits
 - ... and 12 more: https://git.openjdk.org/jdk/compare/cf66820f...c8fdb74c

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/20754/files
  - new: https://git.openjdk.org/jdk/pull/20754/files/5923f361..c8fdb74c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20754&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20754&range=00-01

  Stats: 33684 lines in 970 files changed: 20184 ins; 7746 del; 5754 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