add jdk26 profiles - #19296

stackoverflow.com now enforces Cloudflare bot protection: requests
without a User-Agent get 403, and the /questions page requires a JS
challenge that no plain HTTP client can pass. Add a User-Agent header
to the never-redirect test and repoint the always-redirect test at
httpbin.org/redirect-to.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

…ckoverflow.com

Same Cloudflare bot-mitigation issue as the redirect tests: stackoverflow.com/questions
now returns 403. Point the HTTP/2 check at www.baeldung.com, which reliably serves HTTP/2.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

…low.com dependency

Same Cloudflare bot-mitigation risk as the other HttpClient tests: stackoverflow.com's
/questions page can return a JS challenge instead of 200. Point at httpbin.org/redirect-to,
which mirrors the http->https redirect behavior reliably.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

httpbin.org is currently returning 503 for all endpoints, so the test
gets a 503 instead of 200. Switch to postman-echo.com, already used
reliably elsewhere in this test file.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

…g dependency

httpbin.org is currently returning 503s for all endpoints, making this
test flaky. Switch to postman-echo.com, consistent with the other
HttpClient redirect tests.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>