Right now we have the exporter sender SPI under private folders:
https://github.com/open-telemetry/opentelemetry-java/blob/main/exporters/common/src/main/java/io/opentelemetry/exporter/internal/grpc/
And
https://github.com/open-telemetry/opentelemetry-java/blob/main/exporters/common/src/main/java/io/opentelemetry/exporter/internal/http/

We should allow frameworks to create their own senders and use an official SPI for it.

Describe the solution you'd like
Publicly support the SPI, classes and interfaces under the above packages.

Additional context
There are many sender implementations already. One example is Quarkus, which has implemented a Vert.x client based sender.
Wildfly will use it as well and other application servers will also have the same need.