batch-submitter: default tx batch validation to false

Update the batch validation config parsing so
that the tx batch validation is false by default.
This means that to enable transaction batch validation,
the env var `VALIDATE_TX_BATCH` must be explicitly set
to `true`. If it is not set, then it will default to false.
The logic is shown below for the implementation.

```js
> '' ? '' === 'true' : false
false
> 'false' ? 'false' === 'true' : false
false
> 'true' ? 'true' === 'true' : false
true
```

.changeset/curvy-mirrors-heal.md

+---
+'@eth-optimism/batch-submitter': patch
+---
+
+Default tx batch validation to false

packages/batch-submitter/src/batch-submitter/tx-batch-submitter.ts

@@ -82,6 +82,11 @@ export class TransactionBatchSubmitter extends BatchSubmitter {
     this.autoFixBatchOptions = autoFixBatchOptions
     this.gasThresholdInGwei = gasThresholdInGwei
     this.transactionSubmitter = transactionSubmitter
+
+    this.logger.info('Batch validation options', {
+      autoFixBatchOptions,
+      validateBatch
+    })
   }
 
   /*****************************
@@ -267,6 +272,7 @@ export class TransactionBatchSubmitter extends BatchSubmitter {
     // modify the batch unless an autoFixBatchOption is set
     batch = await this._fixBatch(batch)
     if (this.validateBatch) {
+      this.logger.info('Validating batch')
       if (!(await this._validateBatch(batch))) {
         this.metrics.malformedBatches.inc()
         return
@@ -562,12 +568,15 @@ export class TransactionBatchSubmitter extends BatchSubmitter {
     // NOTE: It is unsafe to combine multiple autoFix options.
     // If you must combine them, manually verify the output before proceeding.
     if (this.autoFixBatchOptions.fixDoublePlayedDeposits) {
+      this.logger.info('Fixing double played deposits')
       batch = await fixDoublePlayedDeposits(batch)
     }
     if (this.autoFixBatchOptions.fixMonotonicity) {
+      this.logger.info('Fixing monotonicity')
       batch = await fixMonotonicity(batch)
     }
     if (this.autoFixBatchOptions.fixSkippedDeposits) {
+      this.logger.info('Fixing skipped deposits')
       batch = await fixSkippedDeposits(batch)
     }
     return batch

packages/batch-submitter/src/exec/run-batch-submitter.ts

@@ -247,7 +247,7 @@ export const run = async () => {
 
   const VALIDATE_TX_BATCH = config.bool(
     'validate-tx-batch',
-    env.VALIDATE_TX_BATCH ? !!env.VALIDATE_TX_BATCH : true
+    env.VALIDATE_TX_BATCH ? env.VALIDATE_TX_BATCH === 'true' : false
   )
 
   // Auto fix batch options -- TODO: Remove this very hacky config