Harden OpenTelemetry install flow

[christopherkarani]

Summary:

• guard the install path with a small state machine so a failure leaves Terra ready to install again
• keep metrics working with a global provider when Terra isn’t explicitly given one
• add concurrency and install coverage that validates meter fallback and tracing-disabled behavior

Testing:

• Not run (not requested)

[christopherkarani]

Superseded by #15, which consolidates the still-valid changes from the current open PR set onto main and intentionally skips stale or conflicting churn.