feat: support continuing on err in beatsauthextension

[pkoutsovasilis]

Summary / What does this PR do?

This PR teaches beatsauthextension to optionally continue running when its HTTP/TLS configuration is invalid, while still surfacing the failure via the OTel component status API and propagating the error to dependent exporters.

Key changes

• Adds continue_on_error to the extension config.
  • When true, the extension does not fail Collector startup; it reports a PermanentError via component status and exposes a RoundTripper that returns the captured error on use.
  • When false (default), startup fails as before.
• Reports status via componentstatus so healthcheckv2 / status endpoints can reflect extension health.
• Refactors HTTP client construction to separate client creation, startup status reporting, and RoundTripper provisioning.

This preserves clarity (like Beats subprocesses) without taking down the whole Collector process.

Why is it important?

Using Beats HTTP transport for the Elasticsearch exporter means a bad TLS/auth config currently causes the entire Collector to exit during extension creation, obscuring which output/config failed. We need to:

• Keep the process alive (especially under Hybrid Elastic Agent).
• Surface failures in a way that maps back to the originating output.
• Let the exporter go unhealthy when it actually attempts to use the extension’s transport.