fix: update semcov dependency and fix minor bugs

[rmarra]

Fixes #9571.

This PR fixes the documentation issues reported in #9571 in the Build a receiver tutorial (content/en/docs/collector/extend/custom-component/receiver.md).

What was fixed

• Updated semconv usage to match go.opentelemetry.io/otel/semconv/v1.38.0:
• Replaced invalid semconv.Attribute* constants with *Key and enum value patterns.
• Fixed cloud provider mapping logic in fillResourceWithBackendSystem():
• Azure/GCP checks now correctly use backend.CloudProvider (instead of backend.OSType).
• Fixed off-by-one loop in generateTraces():
  i <= numberOfTraces -> i < numberOfTraces.
• Removed deprecated rand.Seed(time.Now().UnixNano()) from getRandomNumber().
• Replaced stale semantic conventions reference to Collector semconv source with the correct OTel semconv package docs.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: rmarra / name: Raphael Marra (fefd036)

[theletterf]

@open-telemetry/collector-approvers Please have a look, thanks!

[vitorvasc]

/fix:all

[otelbot-docs]

✅ fix:all applied successfully in run 24040173934.

[dmathieu]

This PR deletes a blog post file when it shouldn't.

[jade-guiton-dd]

Other than the deleted blog post Damien mentioned (which seems to be from the fix:all auto-commit so maybe it's expected?), this looks good to me on the Collector side. Thank you for keeping things up-to-date!

[rmarra]

Guys, I’ve removed the deletion commit and forced a rebase. As @jade-guiton-dd mentioned, it was introduced by fix:all. Should I have left it in?