[exporter/otlp] Improve endpoint validation

[TylerHelmuth]

Is your feature request related to a problem? Please describe.
Currently the otlp exporter's endpoint validation only checks that the endpoint has :PORT and that PORT is an integer. This does not handle situations like:

• port in the wrong place: https://my-backend/v1/traces:4317
• invalid dns endpoint: dns://my-backend:4317

Describe the solution you'd like
Add more intelligent endpoint validation that can detect these errors.

Additional context
These are both situations I've seen customer using the collector experience.

[wasim-nihal]

Hello @TylerHelmuth! I would like to work on improving this endpoint validation. Is this open for contribution?

[TylerHelmuth]

@wasim-nihal yes