drop support for Coq 8.10

Closes #388

See merge request !603

Fix TESTFILES generation on macOS

See merge request iris/iris!604

BSD's find adds an extra / when invoked on tests/, and this confuses the
test dependency management.

Add missing `Hint Mode` for `ghost_var` and `gset_bij`; fix arguments of `gset_bijG`

See merge request !601

Also put the arguments of `gset_bijG` in the right order.

mono_nat_update: make first argument implicit

See merge request !600

Implement monotone partial bijections as a view

See merge request !543

This is an alternative to !91, which was written prior to views. Using
the view CMRA we factor the implementation into purely algebraic library
and a logic-level wrapper. The logic-level wrapper exports resources
which seal away the underlying ownership and has theorems which handle
the ownership reasoning.

Rename `mnat`/`mnat_auth` into `mono_nat`.

See merge request iris/iris!572

Remove the weaker version with the `_lb` since the stronger version is just
as easy to use in the proofmode.

- This avoids confusion between `mnat` and `max_nat`. The `m` stands for `mono`.
- With `_mono` added, the `_auth` suffix in the algebra name no longer makes
  sense, so I removed it.
- This makes the names between the logic and the algebra-level library consistent.
- I also renamed `_frag` into `_lb` in the algebra-level library so as to make it
  consistent with the logic-level library.

Furthermore make the order of lemmas consistent and make the versions for the
fractions consistent.