Validate profiles_endpoint and otlp_http exporter names in endpoint validator

[OisinMcMenamin]

Description of the issue

The otlphttp exporter endpoint validator restricts endpoint, metrics_endpoint,
traces_endpoint, and logs_endpoint to AWS domains, so the agent cannot be
configured to ship telemetry to a non-AWS destination. Two endpoint keys are not
covered: profiles_endpoint, and any endpoint on an exporter keyed with the
otlp_http type name.

Description of changes

• Adds profiles_endpoint to the set of otlphttp exporter endpoint keys checked
  against the AWS DNS-suffix allowlist, so it is validated exactly like the other
  four signal endpoints.
• Matches the exporter type as otlp_http in addition to otlphttp. The
  exporter translator derives its component key from the factory type
  (component.NewIDWithName(t.factory.Type(), name)), so covering both names
  keeps the allowlist applied regardless of which name the vendored collector
  registers.
• Selects exporters by splitting the component key on / and comparing the type
  exactly, matching the convention used in cmd/amazon-cloudwatch-agent/merge.go.
  Near-miss names such as otlphttpx are not matched.

Configurations that do not set profiles_endpoint are unaffected. A non-AWS
profiles_endpoint, and a non-AWS endpoint on an otlp_http-keyed exporter,
are now rejected at startup, consistent with the existing signal endpoints.

License

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Tests

Added unit test cases to TestOTLPHTTPValidator covering, for each of the
otlphttp and otlp_http type names in both bare and named-instance form
(<type>/profiles): a valid AWS endpoint accepted, and a third-party endpoint
rejected. Also added a case asserting a near-miss name (otlphttpx) is not
matched.

Commands run locally:

• go build ./... — clean
• make test — 267 packages pass
• make lint — 0 issues
• make fmt, make fmt-sh — no changes produced
• make check_secrets — reports a match on its own definition in the Makefile;
  reproduces on an unmodified checkout

PR checklist

• Commits are squashed into a logical, reviewable set (one commit for a single change)
• Commits and PR description comply with Amazon internal guidelines
• make passes locally — ran go build ./..., make test, make lint, make fmt, make fmt-sh (see Tests)
• All GitHub Actions checks on the PR are passing
• Integration test evidence: N/A — the change only affects validation during config loading and adds no runtime pipeline behavior; covered by unit tests
• New or updated integration test coverage: N/A — no new integration surface
• New functionality has unit tests; bug fixes have a reproducing test
• Config translation changes include updated golden files: N/A — no translator changes
• Breaking or customer-visible changes are called out in the PR description