treasury_withdrawals endpoint: extend it to include data for activated govActionProposals of type 'treasury withdrawal'

[hodlonaut]

Currently the endpoint only returns information about MIR withdrawals from treasury

On some of the testnets this yields an empty array of data being returned, however across all main networks there're treasury withdrawal gov action proposals that have been ratified and subsequently activated and we should for consistency include details of them (epoch, destination stake address, amount) within this endpoint's implementation