add poke_deposit extrinsic to pallet-proxy (#7801)

# Description

* This PR adds a new extrinsic `poke_deposit` to `pallet-proxy`. This
extrinsic will be used to re-adjust the deposits made in the pallet to
create a proxy or to create an announcement.
* Part of #5591 

## Review Notes

* Added a new extrinsic `poke_deposit` in `pallet-proxy`.
* This extrinsic checks and adjusts the deposits made for either
creating a proxy or creating an announcement or both.
* Added a new event `DepositPoked` to be emitted upon a successful call
of the extrinsic.
* Although the immediate use of the extrinsic will be to give back some
of the deposit after the AH-migration, the extrinsic is written such
that it can work if the deposit decreases or increases (both).
* The call to the extrinsic would be `free` if an actual adjustment is
made to the deposit for creating a proxy or to the deposit for creating
an announcement or both and `paid` otherwise (when no deposit is
changed).
* Added a new enum `DepositKind` to differen...