feat(insight): add HttpExporter

[wangyb-A]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Issue Link, if available

Related: #679

Description

This adds HttpExporter to the Workflow Insight plugin. It sends one insight record to an HTTP endpoint as one request. It mirrors the JS HttpExporter so the two SDKs behave the same.

What it does:

• Sends the record with POST or PUT. POST is the default.
• Sets Content-Type: application/json. A caller may pass their own headers, including their own Content-Type. The caller's value wins. Header names are matched without caring about upper or lower case, so a lowercase content-type replaces the default instead of adding a second one. The endpoint receives exactly one Content-Type header.
• Waits at most timeoutMs for the endpoint. The default is 10000 ms. A non-2xx reply throws.
• Shapes the body with operationsFormat: ARRAY (the default) writes the operations array, BY_NAME writes the operationsByName map, BOTH writes both. render() builds the shape and export() sends it, sharing one path.

How it talks HTTP:

• It uses the JDK's own java.net.http.HttpClient. This adds no new dependency. The client sits behind a small package-visible HttpSender seam so tests can inject a fake, the same way S3Exporter and CloudWatchLogsExporter allow a .client(...).
• It never copies the server's response body into a log. A failure throws with the numeric status and a derived reason label only. This is on purpose: an arbitrary response body could carry sensitive server content.

No change to the SDK core or the Workflow Insight plugin wiring.

Demo/Screenshots

N/A. This is a backend Java change with no user-visible UI, so there is nothing to screenshot.

Checklist

• I have filled out every section of the PR template
• I have thoroughly tested this change

Testing

Unit Tests

Yes. HttpExporterTest (17 tests) covers, with a mock sender: default POST + Content-Type + array body + 10s timeout; PUT with a merged Authorization header; non-2xx throws; BY_NAME map; BOTH array + map; a configured timeout is applied; the caller's Content-Type overrides the default case-insensitively with no duplicate; and builder rejects a missing url, a non-http scheme, a non-absolute url, and a non-positive timeout.

Integration Tests

Transport-level tests run the real default JDK sender end to end against an in-process com.sun.net.httpserver.HttpServer: a POST returns 200 and the handler asserts method, Content-Type, and body; a 500 throws; a PUT with a custom Authorization header is received; the wire carries exactly one Content-Type when the caller overrides its casing; a connection to a dead loopback port throws IllegalStateException; and an interrupted export throws while restoring the thread's interrupt flag.

Examples

N/A. No new example is needed for a new exporter class; the plugin README's HttpExporter section documents customer usage.

[wangyb-A]

Intent: Add an HttpExporter to the Workflow Insight plugin that POSTs/PUTs one insight record as JSON to a generic HTTP endpoint, mirroring the JS SDK's HttpExporter, using only the JDK HttpClient (no new dependency).
Not a goal: No retry/backoff, no response-body logging, no SDK-core or Workflow Insight wiring changes, and no promotion of a toBothWireMap() to core.