Move Uniques Pallet Calls to Internal Functions

[HashWarlock]

For downstream development, we should allow them to utilize the internal functions instead of the user facing functions. This helps avoid the error checks that can be placed in the user facing functions & allow for downstream implementations to call internal functions for dapps that may not need to check ownership.

The general principle is:

• Internal functions bypass permission checks
• User facing functions do permissions checks and call internal function
• Internal functions update storage, call Uniques internal functions and emit an Event.

The following should be changed:

• RMRK Core Pallet
  • burn_nft
  • destroy_collection
  • send
  • accept_nft
  • change_collection_issuer
• Events moved for the rest of usr facing functions