Add `f_equiv/=` which performs `simpl` first.

This is similar to `f_equal/=`.
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Status Job ID Name Coverage
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passed #5195
fp-timing
build-coq.8.6

00:02:04

passed #5194
fp-timing
build-coq.8.6.1

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passed #5193
fp-timing
build-coq.8.7.0

00:02:02

passed #5192
fp-timing
build-coq.8.7.dev

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opam

00:00:13