feat(azure_blob sink): support blob index tags and metadata

[Danielku15]

Summary

Adds blob tags and metadata support to the azure_blob sink. This updates request building and Azure common config handling so tags/metadata are forwarded correctly, and adds unit + Azurite-backed integration coverage for the new behavior.

Vector configuration

Example config used during testing:

sinks:
  azure_blob:
    type: azure_blob
    inputs:
      - my_source
    connection_string: ${AZURE_STORAGE_CONNECTION_STRING}
    container_name: logs
    blob_prefix: vector/
    encoding:
      codec: text
    tags:
      env: prod
      team: platform
    metadata:
      source: vector
      region: us-east-1

How did you test this PR?

Ran:

• cargo fmt --all --check
• cargo clippy --no-default-features --features sinks-azure_blob --tests -- -D warnings
• cargo test --no-default-features --features sinks-azure_blob azure_blob_build_request_with_blob_ -- --nocapture
• cargo test --no-default-features --features sinks-azure_blob,azure-blob-integration-tests sinks::azure_blob::integration_tests:: -- --nocapture
• cargo vdev check generated-docs
• cargo vdev check markdown
• ./scripts/check_changelog_fragments.sh

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

Closes: #22316

Notes

No notes from my side.

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[Danielku15]

I have read the CLA Document and I hereby sign the CLA