otelcolbuilder uses deprecated flags, README.md out of date

[echlebek]

The sands of time have rendered some of the flags that otelcolbuilder is passing to the collector builder obsolete. Additionally, README.md has become out of date now that we have moved from the opentelemetry-collector-builder repo to the collector builder that is in the core repository.

Bring our use of the builder in line with the current state of things. Specifically, fix the following deprecation warnings:

Flag --go has been deprecated, use config distribution::go
Flag --version has been deprecated, use config distribution::version
Flag --output-path has been deprecated, use config distribution::output_path

[echlebek]

Blocked on open-telemetry/opentelemetry-collector#8239