Support custom `@opentelemetry/instrumentation-http` config

[mydea]

We ship our own config for @opentelemetry/instrumentation-http, with some important custom config needed to make Sentry work properly.

However, this means that users cannot use a custom config for this instrumentation.

We should allow users to pass their own config into our integration somehow.

We should provide some curated options that we figure is important, and add an escape hatch to add other config (e.g. _experimental: { instrumentationConfig: {...}})