Clarify standards for vendor inclusion criteria.

[austinlparker]

In regards to https://opentelemetry.io/ecosystem/vendors/, there have been some questions arising about what exactly 'Distribution' and 'Native OTLP' mean.

Upon investigation, vendor support is clarified in the specification @ https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/vendors.md; However, this does not align with the columns on that page. That said, this offers some possible paths:

• Update the vendor page to align with the specification (remove 'distribution' and 'native otlp', change to 'supports opentelemetry' and 'implements opentelemetry')
• Update the specification to add greater specificity in categories
• A secret, third option

[cartermp]

I would propose adding the following to "supports opentelemetry"

• By supporting OTLP ingest on their backend directly
• By supporting an OpenTelemetry SDK distribution

And then also updating the table to have this split, if appropriate.

[cartermp]

While we're at it, we should also decide if we consider something as "supporting opentelemetry" if they still require the use of a non-otel component in the middle, like an agent that supports OTLP but emits their vendor-specific data format.