* Remove unneeded begin/end when the loop is a do/while
* Dangling else check passes through statement attributes (bug fix)
* Dangling else check passes through most control flow structures to reduce unneeded begin/end
* Add test case and update changelog

---------

Co-authored-by: qcorradi <q.corradi22@imperial.ac.uk>
Co-authored-by: Zachary Snow <zach@zachjs.com>

* Fixing a bug where always_* are not converted when attributed
* Added tests and updated Changelog for the attributed always_* fix

- Add script to drop parameters from VCDs.
- Bump the version of iverilog used in CI. I couldn't use anything never
  than eab37efb due a pending iverilog issue.
- Standardize around Python 3 in test cases.

- swap 1364-2001 and 1364-2001-noconfig
- fix existing begin_keywords test
- add keyword test suite for all keywords

- The deleted chunk in TFBlock has been unreachable since 57ef23ef. The
  RemoveComments change would make it reachable by dropping the leading
  Null in a task or function body.
- The optimization in TFBlock was unsound because the nested block could
  shadow identifiers used (but not defined) in the tail of the outer
  block.
- The optimization is not clearly necessary, so I'm dropping it for now.
- Expand tf_block test coverage.

- test deprecated flags
- test struct const edge cases
- test implicit net edge cases
- test dump-prefix

These are now kept while still supporting optional trailing commas and
without introducing pass-through inconsistencies.

- fold string literal comparisons
- fold non-decimal bit shifts
- fold non-decimal integer comparisons
- fold decimal bitwise AND and OR
- simplify cast expressions before elaboration
- remove duplicate cast expression traversal
- flatten concatenated numbers in a single pass

- event expressions use Expr over LHS
- stricter AST representation of event controls
- property specs use event expressions directly