doris: add stream load output

[xylaaaaa]

Summary

• add a new doris_stream_load output
• wire the component into community/default builds
• support JSON and CSV payloads, FE -> BE 307 redirect handling, Expect: 100-continue, query-port based connection tests, and FE failover via fe_urls
• promote common Doris Stream Load options into first-class config fields
• add unit coverage for encoding, redirect/failover behavior, promoted header mapping, and connection tests

Validation

• go test ./internal/impl/doris
• go build -o target/redpanda-connect ./cmd/redpanda-connect

Notes

• local demo configs and local docs were intentionally left out of this PR

[Copilot]

Pull request overview

This PR introduces a new Apache Doris Stream Load output (doris_stream_load) and wires it into the community component bundle so it’s available in standard builds.

Changes:

• Adds a new doris_stream_load batch output implementation with FE→BE redirect handling, JSON/CSV encoding, and FE failover support.
• Registers the Doris component in public/components and the plugin catalog.
• Adds unit tests covering encoding, redirects/failover, header mapping, and connection tests.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
public/components/doris/package.go	Adds the public component package that side-effect imports the internal Doris implementation.
public/components/community/package.go	Wires the new Doris public component into the community build import set.
internal/plugins/info.csv	Registers doris_stream_load in the plugin inventory.
internal/impl/doris/output_stream_load.go	Implements the Doris Stream Load output, config parsing/spec, request building, redirect/failover logic, and connection tests.
internal/impl/doris/output_stream_load_test.go	Adds unit tests for encoding, redirects, failover, connection tests, and promoted header behavior.

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