feat(http): add cURL tab to View Results Tree Request panel

[poliakov-alex]

Render the sampled HTTP request as a ready-to-run curl command in a new "cURL" sub-tab next to Raw and HTTP, so it can be copied or shared.

Closes #6375

Description

Adds a cURL tab to the Request panel of the View Results Tree listener, next to the existing Raw and HTTP tabs. It renders the sampled HTTP request as a ready-to-run curl command that can be copied or shared.

The command includes the method (-X), the URL, request headers (-H), cookies (-b), and the request body (--data-raw). Values are single-quoted and shell-escaped so the output is paste-safe.

Connection-specific (hop-by-hop) and curl-managed headers — Connection, Keep-Alive, Proxy-Connection, Transfer-Encoding, Upgrade, Content-Length — are omitted, because reproducing them makes the request fail (e.g. Connection is forbidden in HTTP/2 and produces curl: (92) ... PROTOCOL_ERROR, and a manual Content-Length conflicts with the body curl computes).

The tab is contributed through the existing RequestView service interface (@autoservice), so no wiring changes were needed in RequestPanel.

Motivation and Context

Fixes #6375. Users frequently need to reproduce a sampled request outside JMeter — in a terminal or when handing it to a developer. Today they must reconstruct the curl command by hand from the Raw/HTTP tabs.

How Has This Been Tested?

Added RequestViewCurlTest (8 JUnit tests) covering GET, headers, POST body, header skipping, cookie handling / de-duplication, single-quote escaping, and a null URL.
Ran ./gradlew :src:protocol:http:test, checkstyleMain, checkstyleTest, autostyleJavaCheck — all green.
Manually verified in the GUI: ran an HTTP sampler, opened View Results Tree → Request → cURL, copied the command and executed it in a terminal successfully.

Screenshots (if appropriate):

Types of changes

New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the [code style][style-guide] of this project.
• I have updated the documentation accordingly.

[milamberspace]

Inline notes from a review of the cURL tab (closes #6375). Overall the feature is clean and closely follows the existing RequestViewHTTP sibling; the main functional gap is multipart/file-upload handling.

For context, the original request is #6375.

[vlsi]

Adversarial pass over the cURL tab, on top of @milamberspace's review. I built the branch, ran the existing tests (green), and exercised buildCurlCommand with a probe test plus real curl against a local HTTP server.

The feature is worth having and the SPI integration is clean. Requesting changes for one class of problem: several ordinary samples render a command that looks correct but reproduces a different request from the one JMeter sent. Four inline notes fall into that class.

• Repeated header names are collapsed by parseHeaders (RequestViewCurl#119).
• The X-LocalAddress pseudo-header is copied into the command although it never went on the wire (RequestViewCurl#57).
• HEAD samples render curl -X 'HEAD', which fails or hangs (RequestViewCurl#107).
• Rendered-placeholder bodies reach --data-raw on two non-multipart paths, so the multipart fix @milamberspace asked for will not cover them (RequestViewCurl#139).

The remaining notes are suggestions, not conditions.

Checked and found correct, for the record: single-quote escaping (name=O'Brien reached the server as exactly 12 bytes), -b cookie syntax, @AutoService registration (both views land in META-INF/services), message-key ordering, locale fallback through the parent bundle, and redirect handling (HTTPSamplerBase takes URL, method, headers, and body from the last hop consistently).