core: (attr assembly fmt) add struct directive (pt6)

[n-io]

Add StructDirective that prints parameters as key=value pairs and parses them in any order. Supports struct(params) for all parameters and struct($a, $b) for a subset.

[codecov]

Codecov Report

❌ Patch coverage is 82.35294% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.22%. Comparing base (446f866) to head (0bebfa9).

Files with missing lines	Patch %	Lines
xdsl/irdl/declarative_assembly_format.py	78.94%	5 Missing and 3 partials ⚠️
xdsl/irdl/declarative_assembly_format_parser.py	92.30%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                         Coverage Diff                         @@
##           nicolai/attr-asm-fmt-pt5-params-v2    #5905   +/-   ##
===================================================================
  Coverage                               86.22%   86.22%           
===================================================================
  Files                                     418      418           
  Lines                                   60214    60265   +51     
  Branches                                 6988     7002   +14     
===================================================================
+ Hits                                    51922    51966   +44     
- Misses                                   6687     6691    +4     
- Partials                                 1605     1608    +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[superlopuh]

I like it

[superlopuh]

It would be great to improve the code coverage here also