Feature request: add and ability to fallback to trx burning for energy, if not enough energy

Please add an ability to burn trx for energy if not enough energy available.
That would be useful for people, who only building up their tron investments, and want so save on part of their daily transactions.

Same feature already exists for bandwidth (ENERGY_DELEGATION_MODE_ALLOW_BURN_TRX_FOR_BANDWITH) let's do same for energy, it's relatively easy to implement according to the code.

Thank you