simplify signature initialization for optimization

[lukehinds]

Remove unnecessary lazy loading mechanism for signature compile

This makes the initialization flow singular (__init__ based), which will reduce unneeded lazy loading on first call, and save cycles from calling _ensure_signatures_loaded

2024-12-15T21:47:27.3dZ [info     ] Started server process [49486] module=server pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/.venv/lib/python3.11/site-packages/uvicorn/server.py
2024-12-15T21:47:27.3dZ [info     ] Waiting for application startup. module=on pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/.venv/lib/python3.11/site-packages/uvicorn/lifespan/on.py
2024-12-15T21:47:27.3dZ [info     ] Application startup complete.  module=on pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/.venv/lib/python3.11/site-packages/uvicorn/lifespan/on.py
2024-12-15T21:47:27.3dZ [info     ] Uvicorn running on http://localhost:8989 (Press CTRL+C to quit) module=server pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/.venv/lib/python3.11/site-packages/uvicorn/server.py

<incoming request>

2024-12-15T21:47:33.3dZ [info     ] Loaded 61 signature groups     module=signatures pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/src/codegate/pipeline/secrets/signatures.py
2024-12-15T21:47:33.3dZ [info     ] Compiled 148 regex patterns    module=signatures pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/src/codegate/pipeline/secrets/signatures.py
2024-12-15T21:47:33.3dZ [info     ]
Found secrets:                module=secrets pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/src/codegate/pipeline/secrets/secrets.py
2024-12-15T21:47:33.3dZ [info     ]
Service: Amazon               module=secrets pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/src/codegate/pipeline/secrets/secrets.py
2024-12-15T21:47:33.3dZ [info     ] Type: Secret Access Key        module=secrets pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/src/codegate/pipeline/secrets/secrets.py
2024-12-15T21:47:33.3dZ [info     ] Original: src/codegate/pipeline/secrets/signatures.py: module=secrets pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/src/codegate/pipeline/secrets/secrets.py
2024-12-15T21:47:33.3dZ [info     ] Encrypted: REDACTED<$d4niwf9MeN2YFmNgUO3KyYmoWg8TlI5EkeK2hwQhT+Bt7LzbHbAElgpyU7J44xCJQiHrGdrLxTtoobqL/QRKfbdOolc+9gR6FqqghzWkQmKZcX8=> module=secrets pathname=/Users/lhinds/repos/stacklok/codegate-repos/codegate/src/codegate/pipeline/secrets/secrets.py```