This adds the trait-associated function `name_column` in order to enable
the possibility of the Layouter to store annotations aobut the colums.

This function does nothing for all the trait implementors (V1,
SimpleFloor, Assembly....) except for the `MockProver`. Which is
responsible of storing a map that links within a `Region` index, the
`column::Metadata` to the annotation `String`.

This adds the fn `annotate_lookup_column` for `ConstraintSystem` which
allows to carry annotations for the lookup columns declared for a
circuit within a CS.

This allows to annotate lookup `TableColumn`s and print it's annotation
within the `assert_satisfied` fn.

This has required to change the `ConstraintSystem::lookup_annotations`
to have keys as `metadata::Column` rather than `usize` as otherwise it's
impossible within the `emitter` scope to distinguish between regular
advice columns (local to the Region) and fixed columns which come from
`TableColumn`s.

This allows to ignore the annotation map of the metadata::Region so that
is easier to match against `VerifyFailure` errors in tests.

It was necessary to improve the `prover.verify` output also. To do so,
this required auxiliary types which are obfuscated to any other part of the lib
but that are necessary in order to be able to inject the Column names inside of
the `Column` section itself.
This also required to re-implement manually `Debug` and `Display` for this enum.

This closes zcash#705

Address some leftover TO-DOs & apply code simplifications for nested if
let Some() blocks.

For the `VerifyFailure::ConstraintNotSatisfied` case we want to customly
impl the `Debug` call so that we can print the annotations within the
`VirtualCell`s.

If we hit any other case of `VerifyFailure` we basically send it to
print and be handled by (ideally Display).

The issue is that the call was forwarded to `Debug` impl again which
ended up in an infinite recursive call to the `Debug` method.
See: privacy-scaling-explorations#109 (comment)

This is solved by calling `Display` if we hit a case that is not
`ConstraintNotSatisfied`.