* Add basic setup for multi-PIN

- Reserve the storage keys for maximum of 8 user slots.
- Modify the storage functions to take a slot_id parameter.
- Add the slot_count() customization.
- Assume slot_id as a parameter when needed except these places:
  - Entrance functions of command processing that directly takes the
    command parameter structure. slot_id is set as 0, and will be
    parsed from the parameters when we enable the feature.
  - MakeCredential/GetAssertion/AuthenticatorConfig will take the
    slot_id from active token state when we enable the feature,
    resulting in an `Option<usize>`. Below code will act on the option
    value correctly. When the feature isn't enabled, we're always
    referring to the only PIN slot so set slot_id as Some(0).
  - GetInfo returns verdict of whether PIN is supported and enabled, and
    whether PIN needs to be forced changed. There will be new fields to
    represent those values when the feature is enabled, and the old
    fields will not be populated. So when the feature isn't enabled, we
    can treat slot_id as 0.

Not covered in this commit:
- Unittests for other slots. The existing tests all pass and I plan to
  add unittests for multi-slot case after the codebase allows enabling
  the feature.
- Persisting and checking the slot_id in credentials. This is planned to
  come in the next commit.

* Fix storage and some other style

* Add support for concatenated values

* Switch some storage entries back to multi-entry

* Set bumpalo version for fuzzing (#532)

* maximum working bumpalo version

* explicit comment to explain version locking

* removes incorrect comment

* moves serde version lock to dev dependencies

* removes serde dependencies

* reverts serde removal in crypto library

* Make PIN_PROPERTIES use concatenated storage entry

* Fix bumpalo issue

* Use concatenated storage entry for force_pin_change too

* Fix cargofmt

Co-authored-by: Julien Cretin <cretin@google.com>
Co-authored-by: kaczmarczyck <43844792+kaczmarczyck@users.noreply.github.com>

* Parse slot_id in use from token state

Support switching to multi-PIN feature and making the default slots 8.
But the command to switch to multi-PIN isn't exposed yet because the
implementation isn't ready.

Main change of this commit is to cache the slot_id in use inside token
state, and retrieve it from token state when needed.

* Fix once_cell dependency (#548)

* fixed version of once_cell

* fixes comments

* removes unnecessary fuzz dependency

* Fix styles

Co-authored-by: kaczmarczyck <43844792+kaczmarczyck@users.noreply.github.com>

* Add storage test cases for multi-PIN

* Fixed proc-macro2 version (#550)

* fixes proc-macro2 in dependencies

* adds missing locked versions, and a verbose print for cargo check

* commits Cargo.lock files

* removes unnecessary Cargo.lock entries

* adds missing Cargo.lock

Co-authored-by: kaczmarczyck <43844792+kaczmarczyck@users.noreply.github.com>

* Persist/parse slot_id in/from credential

Persist slot_id into credential_id or the resident credential record
during MakeCredential, and parse it during GetAssertion. Add related
unittests.

* Fix styles

* Move enable_pin_uv back to ctap/mod.rs