Add `Proper`s for maps, and generalise existing ones. Add tests to check that the old ones can be derived.

Rename `option_mbind_proper` → `option_bind_proper` and `option_mjoin_proper` → `option_join_proper`.

Thanks to @jules for pointing out these were missing.

Fixes new Coq master warning deprecated-hint-without-locality.

Code affected by a00d9bd8.

This was inconsistent and not explained before.

This follows iris!387
This closes issue #54.

The `Equiv` instance for the domain is not needed.

This is in preparation for coq/coq#9274.

Adding a hint without a database now triggers a deprecation warning in
Coq master (https://github.com/coq/coq/pull/8987).

The notation was parsing-only and all it did was reorder the arguments for
from_option.  This creates just a needless divergence between what is written
and what is printed.  Also, removing it frees the name for maybe introducing a
function or notation `default` with a type like `T -> option T -> T`.

This followed from discussions in https://gitlab.mpi-sws.org/FP/iris-coq/merge_requests/134

This follows the associativity in Haskell. So, something like

  f <$> g <$> h

Is now parsed as:

  (f <$> g) <$> h

Since the functor is a generalized form of function application, this also now
also corresponds with the associativity of function application, which is also
left associative.

This way, we will be compabile with Iris's heap_lang, which puts ;;
at level 100.

This provides significant robustness against looping type class search.

As a consequence, at many places throughout the library we had to add
additional typing information to lemmas. This was to be expected, since
most of the old lemmas were ambiguous. For example:

  Section fin_collection.
    Context `{FinCollection A C}.

    size_singleton (x : A) : size {[ x ]} = 1.

In this case, the lemma does not tell us which `FinCollection` with
elements `A` we are talking about. So, `{[ x ]}` could not only refer to
the singleton operation of the `FinCollection A C` in the section, but
also to any other `FinCollection` in the development. To make this lemma
unambigious, it should be written as:

  Lemma size_singleton (x : A) : size ({[ x ]} : C) = 1.

In similar spirit, lemmas like the one below were also ambiguous:

  Lemma lookup_alter_None {A} (f : A → A) m i j :
    alter f i m !! j = None ↔️ m !! j = None.

It is not clear which finite map implementation we are talking about.
To make this lemma unambigious, it should be written as:

  Lemma lookup_alter_None {A} (f : A → A) (m : M A) i j :
    alter f i m !! j = None ↔️ m !! j = None.

That is, we have to specify the type of `m`.

See also Coq bug #5712.