Separate knob buggification from general buggification

[Adityakk9031]

Problem
Currently, enabling BUGGIFY in FoundationDB activates all randomized behaviors globally. In non-simulated clusters (e.g., real hardware or large-scale integrations), we often want to test with randomized knob values. However, most knobs must be uniform across all processes in the cluster. Activating global BUGGIFY triggers many other randomized failure behaviors that are not suitable for these environments.

Solution
This PR decouples knob-specific buggification from general system buggification.

Introduced a new Knobs category in BuggifyType.
Created a BUGGIFY_KNOB macro that specifically checks the Knobs buggify state.
Migrated all BUGGIFY calls within knob initialization (flow/Knobs.cpp, fdbclient/ClientKnobs.cpp) to BUGGIFY_KNOB.
Added a new command-line argument --buggify-knobs [on|off] to fdbserver to allow independent control.
Ensured that in simulation, knob buggification follows the standard buggify override for consistency.

Changes

flow/include/flow/Buggify.h: Added KNOBS category and BUGGIFY_KNOB/BUGGIFY_KNOB_WITH_PROB macros.
flow/Knobs.cpp: Replaced BUGGIFY with BUGGIFY_KNOB in global flow knob definitions.
fdbclient/ClientKnobs.cpp: Replaced BUGGIFY with BUGGIFY_KNOB in client knob definitions.
fdbserver/fdbserver.actor.cpp:
Added knobsBuggifyEnabled flag to CLIOptions.
Added --buggify-knobs CLI argument parsing.
Updated main() to toggle knob buggification independently.
Synchronized knobsBuggifyEnabled with buggifyOverride in simulation mode.

[Adityakk9031]

@saintstack sir have a look please