Release v0.9.0

[MrAlias]

This release includes a new Resource auto-detector interface and a generation of the OTLP locally.

Needed for open-telemetry/opentelemetry-proto#173

Added

• A new Resource Detector interface is included to allow resources to be automatically detected and included. (OT resource detector #939)
• A Detector to automatically detect resources from an environment variable. (OT resource detector #939)
• Github action to generate protobuf Go bindings locally in internal/opentelemetry-proto-gen. (Create protobuf generation GitHub action #938)
• OTLP .proto files from open-telemetry/opentelemetry-proto imported as a git submodule under internal/opentelemetry-proto. References to github.com/open-telemetry/opentelemetry-proto changed to go.opentelemetry.io/otel/internal/opentelemetry-proto-gen. (Import open-telemetry/opentelemetry-proto submodule and generate protobuf bindings locally #942)

Changed

• Non-nil value structs for key-value pairs will be marshalled using JSON rather than Sprintf. (supports marshaling values as json #948)

Removed

• Removed dependency on github.com/open-telemetry/opentelemetry-collector. (Remove github.com/open-telemetry/opentelemetry-collector dependency #943)