drop support for Coq 8.10

Closes #388

See merge request iris/iris!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 iris/iris!601

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

mono_nat_update: make first argument implicit

See merge request iris/iris!600

Implement monotone partial bijections as a view

See merge request iris/iris!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.