kaiax/builder: Introduce TxOrGen

[ian0371]

Proposed changes

• Now gasless module initializes TxGenerator hash with ApproveTx.Hash || SwapTx.Hash. Previously, hash was initialized at incorporate lazily, which resulted in TxGenerators having incorrect hashes. TxGenerator's type is reverted back to function.
• Introduce TxOrGen; it replaces []interfaces{} array from builder. txOrGen can be evaluated to tx by GetTx(nonce).
• Change Has(hash common.Hash) -> Has(txOrGen *TxOrGen). To find by hash, FindIdx(id common.Hash) can be used.
• Lambda functions are introduced in worker, such as markAllTxUnexecutable.
• Fix tests/kaia_test_account_map_test.go so txOrGen is evaluated to tx in the correct order.

Types of changes

• Bugfix
• New feature or enhancement
• Others

Checklist

• I have read the CONTRIBUTING GUIDELINES doc
• I have read the CLA and signed by comment I have read the CLA Document and I hereby sign the CLA in first time contribute
• Lint and unit tests pass locally with my changes ($ make test)
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules