refactor: Removing dead code and making patch task more generic

[bdchatham]

Summary

Redesigns the config-patch system as a generic TOML merge-patch mechanism and removes dead code across the seictl task implementations.

• Generic config-patch: ConfigPatchTask now carries a Files map[string]map[string]any where keys are filenames (e.g. config.toml, app.toml) and values are arbitrary nested patches. The server-side ConfigPatcher applies each via recursive merge, replacing the old hardcoded PatchSet/parsePatchSet approach.
• Direct config writes: discover-peers and configure-state-sync now write directly to config.toml via mergeAndWrite, eliminating the intermediate .sei-sidecar-peers.json and .sei-sidecar-statesync.json files and their readers.
• Snapshot extract fix: Snapshot restoration now extracts to data/snapshots/ instead of the home directory root.
• Dead code removed: signal.go, updatepeers.go, updatepeers_test.go, the legacy {region, chainId} param format in peer discovery, ReadPeersFile, ReadStateSyncFile, and SnapshotGenerationPatch.
• Shared types: Extracted tendermintStatusResponse and tendermintBlockResponse into tendermint.go.
• Bug fix: writeUploadState now propagates errors instead of silently swallowing them.

Files removed

• sidecar/tasks/signal.go
• sidecar/tasks/updatepeers.go
• sidecar/tasks/updatepeers_test.go