[Deprecation] Treasury Proposals and spend_local call

[muharem]

Deprecate the items related to the Gov_v1 treasury spend flow and provide an implementation of the Pay trait within the treasury pallet to make it possible to setup the spend call to work as spend_local.

Deprecated items:

• Proposals, ProposalCount and Approvals storage items;
• spend_local and remove_approval calls;
• all public items associated exclusively with above items (e.g. MaxApprovals);

Reference issue: #138

Tasks

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1. Hard deprecation by adding a warning message
2. Remove usage of the deprecated feature in the code base
3. Update examples and tutorials
4. Deprecation is noted in the release log
5. Removal version is planned
6. Deprecated feature is removed
7. Removal of the feature is noted in the release log

[muharem]

The PR deprecating the public items should have the implementation of Pay trait that implemented over fungible trait. This implementation should allow to setup the spend call to behave as spend_local, transferring the funds locally. The PRdoc should contain instructions on how to migrate to the spend and stop using the spend call.

[davidk-pt]

I think there's already config of Paymaster inside treasury pallet, we need to add another one? Am I missing something?

		/// Type for processing spends of [Self::AssetKind] in favor of [`Self::Beneficiary`].
		type Paymaster: Pay<Beneficiary = Self::Beneficiary, AssetKind = Self::AssetKind>;