Remove EnableFastCommit option (always enabled)

[vazois]

Summary

Remove the EnableFastCommit server option and make the codebase always operate in FastCommit mode.

Changes

• Remove EnableFastCommit field from GarnetServerOptions, Options, and defaults.conf
• Hardcode FastCommitMode = true in TsavoriteLog settings
• Remove all dead-code paths gated on !EnableFastCommit (manual commits in replica sync, failover, recovery, cluster truncation)
• Simplify commit task in StoreWrapper and DatabaseManagerBase
• Remove fastCommit parameter from test utilities and cluster test contexts
• Update website configuration documentation

Motivation

EnableFastCommit has defaulted to true everywhere (server, tests, benchmarks) and the non-fast-commit path was effectively dead code. Removing it simplifies the AOF/replication logic and eliminates a configuration footgun.

[Copilot]

Pull request overview

This PR removes the EnableFastCommit server option and simplifies the AOF/replication/recovery codepaths by making FastCommit mode always enabled for TsavoriteLog-based AOF.

Changes:

• Removes EnableFastCommit from configuration surfaces (CLI options, defaults, server options) and related validation/guards.
• Forces TsavoriteLogSettings.FastCommitMode = true and removes non-fast-commit branches in cluster replication/sync/recovery/truncation flows.
• Updates test utilities and cluster test contexts to drop the fastCommit parameter/argument and removes associated test branching.

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
website/docs/getting-started/configuration.md	Removes the EnableFastCommit configuration entry from docs.
test/standalone/Garnet.test/TestUtils.cs	Drops fastCommit parameter plumbing from test server/cluster helpers.
test/Garnet.fuzz/Targets/GarnetEndToEnd.cs	Removes EnableFastCommit from fuzz target server options.
test/cluster/Garnet.test.cluster/ClusterTestContext.cs	Removes FastCommit parameter from cluster test context APIs and calls.
test/cluster/Garnet.test.cluster/ClusterManagementTests.cs	Removes FastCommit argument from cluster management test setup.
test/cluster/Garnet.test.cluster.replication/ReplicationTests/ClusterReplicationBaseTests.cs	Removes fast-commit toggling from replication tests; exercises the always-fast-commit behavior.
libs/server/StoreWrapper.cs	Simplifies commit background task behavior by skipping commits on replicas unconditionally.
libs/server/Servers/GarnetServerOptions.cs	Removes EnableFastCommit field; hardcodes FastCommitMode = true and always applies throttle freq.
libs/server/Databases/DatabaseManagerBase.cs	Simplifies compaction-time AOF commit logic (no replica commit path).
libs/server/AOF/Recover/RecoverLogDriver.cs	Removes non-fast-commit guard/exception for fast-commit metadata records during replay.
libs/server/AOF/GarnetLog.cs	Removes assertion that sharded-log requires FastCommit option.
libs/host/defaults.conf	Removes default config entry for EnableFastCommit.
libs/host/Configuration/Options.cs	Removes CLI option parsing/mapping/validation for --fast-commit.
libs/cluster/Server/Replication/ReplicationHistoryManager.cs	Removes non-fast-commit failover commit/wait path.
libs/cluster/Server/Replication/ReplicaOps/ReplicaDisklessSync.cs	Removes non-fast-commit commit/wait before replay reset.
libs/cluster/Server/Replication/ReplicaOps/ReplicaDiskbasedSync.cs	Removes non-fast-commit commit/wait before replay reset.
libs/cluster/Server/Replication/ReplicaOps/AOFReplay/ReplicaReplayTask.cs	Removes non-fast-commit guard/exception when receiving fast-commit metadata records.
libs/cluster/Server/Replication/ReplicaOps/AOFReplay/ReplicaReplaySession.cs	Always enqueues replica stream records with noCommit: true (fast-commit path).
libs/cluster/Server/Replication/ReplicaOps/AOFReplay/ReplicaReplayDriver.cs	Removes non-fast-commit guard/exception on fast-commit metadata records.
libs/cluster/Server/ClusterProvider.cs	Removes non-fast-commit commit after AOF truncation.
benchmark/Resp.benchmark/OfflineBench/AOFBench/AofGen.cs	Removes EnableFastCommit from benchmark AOF server options.