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 featureFlagQETextSearchPreview to use the operation FCV-aware checks.

Background
The featureFlagQETextSearchPreview is used in processFieldsForInsert() within fle_crud.cpp.
There is no opCtx passed down to this function, and there are many code paths that lead to it e.g. processInsert(), processUpdate() .
Moreover, some codepaths invoke the function through a callback when running transactions.
All of this makes it non-trial to adapt featureFlagQETextSearchPreview to use the updated API.

Goal
The goal of this ticket is to:

1. Switch featureFlagQETextSearchPreview to use the new FCVGatedFeatureFlag API by removing the fcv_context_unaware parameter from its idl specification.
2. Explore ways to make checking featureFlagQETextSearchPreview 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.