fix(client-certificates): errors during http2 TLS handshake

[mxschmitt]

Investigation: Currently when a TLS handshake error happens on a http2 connection, the response gets corrupted. This is because:

1. The client (browser, internalTLS) sends a http2 handshake to our proxy
2. The target connection emits a secureConnect event
3. We attach listeners since we received secureConnect event and send the buffered "client hello" data over
4. The target connection emits an error event
5. We try to send a http2 response over but the client (browser) already received some parts of the handshake and is confused. This ends up in Error: Received bad client magic byte string and net::ERR_HTTP2_PROTOCOL_ERROR.

This brought up that using the session event seems to be the right one for our use-case.

Relates playwright-community/playwright-go#480
Example error: https://github.com/playwright-community/playwright-go/actions/runs/10465991368/job/28982096640?pr=480#step:6:166

[github-actions]

Test results for "tests 1"

3 failed
❌ [firefox-page] › page/page-goto.spec.ts:182:3 › should properly cancel Cross-Origin-Opener-Policy navigation
❌ [webkit-library] › library/modernizr.spec.ts:33:3 › safari-14-1
❌ [webkit-library] › library/modernizr.spec.ts:83:3 › mobile-safari-14-1

2 flaky

⚠️ [firefox-page] › page/frame-goto.spec.ts:46:3 › should continue after client redirect
⚠️ [playwright-test] › ui-mode-test-progress.spec.ts:22:5 › should update trace live

30093 passed, 870 skipped
✔️✔️✔️

Merge workflow run.