MvP-4443 Cleanup checkOutputs

[ctnguyen]

TxValidator.go:328 output.LockingScript.IsP2SH() is done inside VerifyScript

TxValidator.go:341 check spendable and dust

• isUnspendableOutput is done in bsv Solver, which is called inside bdk for standardness check
• check dust limit is done in IsStandardTx, which is called inside bdk for standardness check

TxValidator.go:232 pushDataCheck is done inside VerifyScript

[ctnguyen]

Grouped to the PR #421

[ctnguyen]

Grouped to the PR #421