[code-reflection] RFR: Implement bitwise/shift assignment operations

[Hannes Greule]

This change adds support for compound assignments for bitwise operations and shift operations. Tests are also enhanced to cover those cases.

As with already existing operations, input types `byte`, `char`,  `short` are not converted to `int`. Again, we have the special case of shift operations where the spec dictates unary promotion. That's why currently the rhs is promoted to `int` even in shift compound assignments.

The additional methods in `InvokableLeafOps` are needed in the current design.

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Commit messages:
 - Implement bitwise/shift assignment operations

Changes: https://git.openjdk.org/babylon/pull/77/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=77&range=00
  Stats: 261 lines in 4 files changed: 242 ins; 1 del; 18 mod
  Patch: https://git.openjdk.org/babylon/pull/77.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/77/head:pull/77

PR: https://git.openjdk.org/babylon/pull/77