Thanks to @tchajed for pointing out the omission.

Various improvements to `Permutation` lemmas and instances

See merge request iris/stdpp!270

Rename `Permutation_nil` and `Permutation_singleton` into `Permutation_nil_r` and `Permutation_singleton_r`.

Add lemmas `Permutation_nil_l` and `Permutation_singleton_l`.

Naming scheme: `operation_Permutation_{Proper,inj,inj_l,inj_r}`.

Comment about `EqDecision` in `Countable`.

See merge request !268

Thanks to @jules for pointing out these were missing.

Explicit visibility for Instances

See merge request !263

This reverts commit 267cc708.

Thanks to @jung for spotting this was a NOP, see !263 (comment 67379)

list lookup lemmas: cons, singleton

See merge request !264

explicitly declare visibility of Scope actions

See merge request !262