Add BurnPolicies similar to MintPolicies

[onurinanc]

As part of the work on Regulated Fungible Tokens, we will also be developing support for Burnable tokens. We currently have MintPolicy in place (without having the MintPolicyManager as a separate account component), and as part of this effort I propose introducing a BurnPolicies while preserving the same overall structure.

As we decide to go with the MintPolicyManager follow-up PR for the mint policies, and likewise we might not introduce a BurnPolicyManager at this stage, and combine them in one-follow up PR when introducing role-based access control.