Specifically, support has been added for non-ANSI style port
declarations where the port declaration is separate from the
corresponding net or variable declaration.

- all inputs are now decoded as UTF-8, regardless of the platform
- decoding failures are now tolerated via transliteration given errant
  characters are generally expected to appear in comments

This works around a compilation performance regression in GHC 9.0.1:
https://gitlab.haskell.org/ghc/ghc/-/issues/20261. This also speeds up
compilation on other versions.

This adds support for typed valued parameters declared in parameter port
lists without explicitly providing a leading `parameter` or `localparam`
marker.

- use iverilog's -gstrict-expr-width throughout test suite
- add warnings for excess bits or padding zeroes in number literals
- add new --oversized-numbers parameter to retain support for unsized
  numbers wider than 32 bits
- localized use of oversized numbers to new truncate test suite which
  verifies the behavior of both modes, and compares against the known
  behavior of iverilog

- detect and forbid non-positive size casts
- detect and forbid negative struct pattern literal indices
- avoid invalid constant folding of negative based literals

- add unified frontend configuration record to make adding future
  options easier
- use ExceptT throughout, rather than using runExceptT at internal
  boundaries

Workarounds for resolved iverilog issues have been removed.

- upgrade to happy 1.20
- placate GHC warning on version fallback
- fix stack sdist failure