[TX] Add remaining platform tx to caminoExecutor (spend / lock)

[c4t-ag]

Camino TX / spend adjustment

PR implements all platformTx from utxoset which use getMinimumSpendable.
Instead the JS based UTXO logic we let camino-node / go evaluate the resulting UTXOs.

[Chriserus]

LGTM

[c4t-ag]

I was not happy because of all the code changes in UTXO and API, so I reworked platform API:
-> move createTx functions from UTXO into new Builder (which can now either get old or new getMinimumSpendable from interface.
-> Create a Builder class which capsulates the spend call into camino-node.

Pls. @Chriserus review again. I'll merge earliest when evgeni has approves the chnages made in caminogo to you can verify that tx work as expected (e.g. RegisterNodeTx, AddValidatorTx, ImportTx and ExportTx).