Summary
SERVER-99351 introduced a new API for the FCV-gated feature flags that checks them against the operation FCV.
To ease the transition, existing feature flag checks were allowed to keep using the old API (specified by fcv_context_unaware: true idl parameter).
This ticket is for converting the featureFlagEndOfTransactionChangeEvent to use the operation FCV-aware checks.

Background
The featureFlagEndOfTransactionChangeEvent is non-trivial to convert since it is used during one of the phases of the TransactionCoordiantor.
In contrast to DDL coordinators, the TransactionCoordinator currently does not use the ForwardableOperationMetadata to propagate opCtx metadata.

Goal
The goal of this ticket is to:

1. Switch featureFlagEndOfTransactionChangeEvent to use the new FCVGatedFeatureFlag API by removing the fcv_context_unaware parameter from its idl specification.
2. Explore ways to make checking featureFlagEndOfTransactionChangeEvent aware of the operation FCV by passing the VersionContext.

Note that the relience on the version context during checks can be bypassed by using one of the dummy values.
This approach will make the feature flag check fallback on the fcv snapshot parameter.
Please use this strategy only when strictly needed, as it might introduce inconsistent behavior if used incorrectly.