[code-reflection] RFR: BytecodeGenerator cleanup and and types handling fixes

[Adam Sotona]

I've narrowed implementation of `BytecodeGenerator` with:
- clear stack handling 
- better code optimization.
- fixed handling of types
- improved test coverage and test failure reporting

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Commit messages:
 - split of canDefer method to avoid redundant dispatching
 - fixed comments
 - long lines breaks
 - BytecodeGenerator work in progress
 - BytecodeGenerator work in progress
 - BytecodeGenerator work in progress
 - BytecodeGenerator work in progress
 - lambda revert
 - Merge branch 'code-reflection' into generator-round-4
 - BytecodeGenerator work in progress
 - ... and 8 more: https://git.openjdk.org/babylon/compare/d02e7c6f...54035024

Changes: https://git.openjdk.org/babylon/pull/58/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=58&range=00
  Stats: 376 lines in 3 files changed: 233 ins; 43 del; 100 mod
  Patch: https://git.openjdk.org/babylon/pull/58.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/58/head:pull/58

PR: https://git.openjdk.org/babylon/pull/58