core: (irdl) Add regions to declarative assembly format

[kimxworrall]

Added support for regions to the declarative assembly format.

The declarative assembly format now supports:

• Referring to region variables
• Referring to optional or variadic region variables
• Printing custom assembly for region variables

The format requires that:

• The attr-dict-with-keyword directive is present and not attr-dict. This is to maintain consistency with mlir.
• The regions appear after the attributes.

Also added tests.

[alexarice]

Could you comment on why regions must come after attributes? I can't see anything about this in the mlir documentation (which doesn't mean it's not true)

[alexarice]

Haven't read through everything but here's some comments

[alexarice]

There's still two files that you've not touched being pulled in somehow. I've left a few minor comments but looking good, will give it a test tomorrow

[alexarice]

I also have no idea why the mlir integration tests are failing

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.90%. Comparing base (5299b90) to head (3ab7c03).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3065      +/-   ##
==========================================
+ Coverage   89.88%   89.90%   +0.02%     
==========================================
  Files         418      418              
  Lines       52764    52913     +149     
  Branches     8175     8202      +27     
==========================================
+ Hits        47426    47571     +145     
- Misses       4013     4015       +2     
- Partials     1325     1327       +2     

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[PapyChacal]

Amazing to see that in!

The implementation and existing tests seem perfect to me, only have some minor polish comments :) Making this an approval as at this point I consider any further polishing a bonus, the feature seems ready to benefit xDSL in itself!

Thanks a lot!

[alexarice]

I've had a little test locally and this seems reasonable. Thanks for implementing this. Happy for this to be merged once the remaining comments are resolved