Add constraints for `^Step` param type in ranges in `(.. ..)` operators

[abelbraaksma]

Description

Using user-defined types with ranges (that is, the .. .. operator as in for x in y .. step .. z do and the like) are required to have comparison and equality constraints. While the definition of (.. ..) has these constraints on the counter type, and it has and default ^Step : ^T, the compiler does not infer from this that this requires the ^Step parameter to have the same constraints.

This should be caught by the compiler as a discrepancy between the *.fsi file and the implementation file.

Without using the constraints on your type, code would compile, but always fail at runtime. See linked issue for details.

Fixes #6238

Checklist

• [x] Test cases added (note: there seem to be ZERO cases for user defined types)
  • [ ] TODO: a few more test cases and ideally a compile-time test case
  • [ ] TODO: fix new test case that's now (deliberately) failing
• [x] Release notes entry updated

[github-actions[bot]]

:heavy_exclamation_mark: Release notes required

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:white_check_mark: Found changes and release notes in following paths:

Change path	Release notes path	Description
src/FSharp.Core	docs/release-notes/.FSharp.Core/8.0.400.md