[Merged by Bors] - perf: make Field input to ClassGroup.mk explicit

[kbuzzard]

I noticed typeclass inference being slow to infer this input, so let's try making it explicit.

This is a way of removing the (W := W) hack introduced in #39124 .

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[github-actions]

PR summary 0b683b8515

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

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No changes to strong technical debt.

No changes to weak technical debt.

[kbuzzard]

!radar

[leanprover-radar]

Benchmark results for 0b683b8 against c669471 are in. No significant results found. @kbuzzard

• ✅ build//instructions: -13.9G (-0.01%)

Small changes (1✅, 2🟥)

• ✅ build/module/Batteries.Data.BitVec//instructions: -20.3M (-1.42%)
• 🟥 build/module/Mathlib.Analysis.Meromorphic.IsolatedZeros//instructions: +297.3M (+3.60%)
• 🟥 build/module/Mathlib.Lean.Name//instructions: +174.8M (+5.57%)

[kbuzzard]

The 14G decrease in instructions is little more than noise -- the point of this PR is that #39124 and #mathlib4 > Field (FunctionField ?m.19) @ 💬 shows that we have a footgun and this PR is an attempt to make it less likely to go off. Note that if you fill in the now-explicit input field with _ then it can still fire. The bottom line is that this

ClassGroup.mk.{u_1, u_2} {R : Type u_1} {K : Type u_2} [CommRing R] [Field K] [Algebra R K] [IsFractionRing R K]
  [IsDomain R] : (FractionalIdeal R⁰ K)ˣ →* ClassGroup R

is not great in Lean 4, and making K explicit is a bit better.

[mattrobball]

bors merge

[mathlib-bors]

Pull request successfully merged into master.

Build succeeded:

• ci (staging) / Lint style
• ci (staging) / Build
• ci (staging) / Post-Build Step
• ci (staging) / Post-CI job