[Merged by Bors] - chore(AddConstMap): don't extend FunLike

[urkud]

Instead, take it as an argument as other bundled homs do.
Also change the npow field in the Monoid instance so that coe_pow is a rfl lemma now.

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[github-actions]

PR summary ac4df7dec2

Import changes

No significant changes to the import graph

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Declarations diff

+ instance : FunLike (G →+c[a, b] H) G H
+ instance : Mul (G →+c[a, a] G) := ⟨comp⟩
+ instance : One (G →+c[a, a] G) := ⟨.id⟩
+ instance : Pow (G →+c[a, a] G) ℕ
+ toFun_eq_coe

You can run this locally as follows

## summary with just the declaration names:
./scripts/no_lost_declarations.sh short <optional_commit>

## more verbose report:
./scripts/no_lost_declarations.sh <optional_commit>

[dupuisf]

Thanks!

bors r+

[mathlib-bors]

Pull request successfully merged into master.

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