core: (attr assembly fmt) add wiring into irdl_param_attr_def (pt2)

[n-io]

Integrate the attr declarative assembly format into the attribute definition system. ParametrizedAttribute subclasses can now set assembly_format = "..." to auto-generate parse_parameters and print_parameters methods.

Stacked on top of: #5900

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.21%. Comparing base (377ba90) to head (875f177).

Files with missing lines	Patch %	Lines
xdsl/irdl/attributes.py	90.90%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@                            Coverage Diff                            @@
##           nicolai/attr-asm-fmt-pt1-core-directives    #5901   +/-   ##
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  Coverage                                     86.20%   86.21%           
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  Files                                           418      418           
  Lines                                         60077    60104   +27     
  Branches                                       6950     6955    +5     
=========================================================================
+ Hits                                          51791    51818   +27     
+ Misses                                         6689     6688    -1     
- Partials                                       1597     1598    +1     

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[superlopuh]

Happy to review this as soon as merge conflicts are resolved.

[Samielakkad]

I think required structural directives are currently too permissive during parsing.

AttrFormatProgram.parse ignores the boolean returned by each directive:

for stmt in self.stmts:
    stmt.parse(parser, state)

but AttrPunctuationDirective.parse and AttrKeywordDirective.parse use optional parsers and only return False when the token is missing. That means a format like:

assembly_format = "$first `,` $second"

may accept an input without the comma, as long as $second can still be parsed afterwards, because the missing punctuation does not raise. The same applies to required keywords.

I think required punctuation/keyword directives should call the non-optional parser variant, or AttrFormatProgram.parse should treat False as an error for non-optional directives. Optional groups can still use parse_optional for the speculative path.