chore: Replace dependency on unexported otelcol functions

[dehaansa]

PR Description

Inspired by #1023 - replacing the call to an unexported function to utilizing the intended functionality from otelcol.

• Tests updated
• Config converters updated

[ptodev]

Amazing, thank you! I didn't realise that it's possible to do this 😆 I thought the public OTel functions only allow generating the config from a file.

[ptodev]

Thank you! Would you like to also do the same change to the Agent?
We won't be able to rid of the fork entirely, but it'll help - there will be less things to modify on the fork when we upgrade it.

[wildum]

@ptodev I don't believe that we are planning on updating the Otel version for the Agent

[ptodev]

I suppose so, but we might have to, you never know :)

[ptodev]

I don't insist on the change being done on the Agent. I'll leave it up to @dehaansa to decide if it's worth his effort. Maybe it's too much risk for too little benefit.

[wildum]

We already use a custom version of the fork for the agent because of some CVEs (see https://github.com/grafana/agent/blob/main/go.mod#L777) so to get rid of the fork we would either need to copy some more code or we would need to upgrade the Otel version at the same time to get the CVEs fix.
I personally don't think that's worth the effort