Instead of the Go autoinst agent appearing to telemetry data receivers
as only the version of grpc-go against which it was built, this adds an
identifier to the User-Agent header via the dial options parameter
support within otlptracegrpc.

To help troubleshooting data transmission, runtime operating system and
CPU architecture is included in the user-agent within a parenthetical
comment in accordance with the header's specification.[1]

This replaces the low-level build up of a gRPC client connection with a
reuse of the OTel Go SDK's grpc trace client constructor. A happy
byproduct of using the SDK's constructor is that all of the
OTEL_EXPORTER_OTLP_* environment variables related to exporting traces
ought to be supported now, obviating the need to maintain code here to
retrieve, interpret, and handle them.

[1] RFC 7231 https://www.rfc-editor.org/rfc/rfc7231#section-5.5.3
    though more readable documentation about this header spec is
    available at MDN Web Docs:
    https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/User-Agent

This is an expendable commit if folks don't like it.

Spec and therefore SDK require the URL scheme in ENDPOINT values.

This Go auto-inst adds its version to resource attributes now.

The version declared here will get bumped when using the multimod
releaser utility.

The agent's controller uses this version to include in the User-Agent
header and in a resource attribute for outgoing telemetry.

Modeled after the test targets in OpenTelemetry Go.

Removes the "maybe use gotestsum if you've got it!" option.

Co-authored-by: Tyler Yahn <[email protected]>

Always Be Testing.

Co-authored-by: Tyler Yahn <[email protected]>