add poke_deposit extrinsic to pallet-bounties

[UtkarshBhardwaj007]

Description

• This PR adds a new extrinsic poke_deposit to pallet-bounties. This extrinsic will be used to re-adjust the deposits made in the pallet to create a new bounty.
• Part of Re-consideration poke for Deposits  #5591

Review Notes

• Added a new extrinsic poke_deposit in pallet-bounties.
• This extrinsic checks and adjusts the deposits made for creating a bounty.
• 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 and paid otherwise (when no deposit is changed).
• Added tests to test all scenarios.
• Added benchmarks

TO-DOs

• Run CI cmd bot to benchmark

[UtkarshBhardwaj007]

/cmd fmt

[UtkarshBhardwaj007]

/cmd prdoc

[UtkarshBhardwaj007]

/cmd bench --pallet pallet_bounties

[github-actions]

Command "bench --pallet pallet_bounties" has started 🚀 See logs here

[github-actions]

Command "bench --pallet pallet_bounties" has finished ✅ See logs here

Subweight results:

File	Extrinsic	Old	New	Change [%]
substrate/frame/bounties/src/weights.rs	poke_deposit		309.04us	Added
polkadot/runtime/rococo/src/weights/pallet_bounties.rs	poke_deposit		314.57us	Added

Command output:

✅ Successful benchmarks of runtimes/pallets:
-- dev: ['pallet_bounties']
-- rococo: ['pallet_bounties']

[kianenigma]

Tests can likely be simplified, but otherwise looks good to me!

[UtkarshBhardwaj007]

/cmd fmt