refactor: make base instruments generic over their config type

[lesnik512]

Fixes #285.

The Cors, HealthChecks, Logging, OpenTelemetry, Prometheus and Swagger instruments each get a config type variable bound to their config class, and each framework instrument binds it:

class FastAPICorsInstrument(CorsInstrument[FastAPIConfig]): ...

Before this, every framework instrument re-annotated bootstrap_config with its own config type, and ty 0.0.87 rejected that as invalid-mutable-override. The 20 ignores #284 added for this are gone. So is an invalid-method-override ignore on LitestarSwaggerInstrument.is_configured: its LitestarConfig parameter is no longer narrower than the parameter it overrides.

Nothing changes at runtime. Out-of-tree subclasses such as class MyCors(CorsInstrument) keep working; ty just sees their config type as unknown until they bind the parameter.

The 5 bootstrapper ignores stay. The issue explains why: making BaseBootstrapper generic over its config would either break BaseBootstrapper[App] or need a typing-extensions TypeVar default.

Locally with ty 0.0.87, just lint-ci is clean and just test-ci passes (362 passed, 100% coverage).