Remove test modules

[pellared]

Follows #6763

What is interesting if the dependency is used only used in tests then it does not come up as an indirect dependency for modules using go.opentelemetry.io/otel/sdk/log 🎉

It looks like the Go module graph pruning has been improved at some point.

I think that it means that we could get rid of test modules 😉

Originally posted by @pellared in open-telemetry/opentelemetry-go#6286 (comment)

Also see https://seankhliao.com/blog/12025-04-07-pruned-module-graph/ that the test dependencies are being pruned.

We already have a golang-ci lint rule no-sdk-instrumentation to make sure that production code does not use the SDK

• Remove semconv/test modules #7445
• Remove otelmux/test module #7448
• Remove otelgrpc/test module #7449
• Remove otelgin/test module #7450
• Remove otelhttptrace/test module #7451
• Remove otelecho/test module #7452
• Remove otelaws/test module #7453
• Remove otellambda/test module #7454
• Remove otelrestful/test module #7455