Simplify artificial delay logic and remove user-based latency

[arafatkatze]

Solves Linear Issue

History:

When working on the Removal of Artificial Latency behind a feature flag Valery said FeatureFlag.CodyAutocompleteUserLatency feature flag and all the related logic is not used anymore and plan on conducting no further experiments with it. So I removed that and a lot of related logic that made this function and its tests very intricate.

This PR does

• Remove user-based latency adjustments and related feature flag
• Simplify getArtificialDelay function to only consider language and completion intent
• Update lowPerformanceConfig to include both language IDs and completion intents
• Remove resetArtificialDelay function and related calls(This function would reset User based latency for when completions were rejected. This stuff is not relevant after the removal of the feature flag)
• Update tests to reflect new simplified logic
• Remove unused LatencyFeatureFlags interface and related parameters

Test plan

Added new tests and made the logic very clean and self explainatory.

Changelog