refactor: rm dependency from x/auth -> x/feegrant

[kocubinski]

Description

Ref: #14649 (review), #14559

Removes the dependency on x/feegrant from x/auth. This is required for x/feegrant as a go module since it (like most modules) depends on x/auth.

• Use expected keeper in ante package instead of keeper interface in feegrant
• Remove unnecessary (or unused) x/feegrant dependencies from test phase.

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[julienrbrt]

lgtm!

[julienrbrt]

I think bez meant here: https://github.com/cosmos/cosmos-sdk/blob/main/testutil/assertHelpers.go
If you end up moving this to this file, could you rename that file too :D