test: use http endpoint instead of local file for codegen tests

[mxschmitt]

Motivation: Our codegen users don't use file:// and this will simplify WSL tests (#36358), since there file:// would require FS path mapping.

[github-actions]

Test results for "tests 1"

6 flaky

⚠️ [firefox-library] › library/inspector/cli-codegen-1.spec.ts:1087:7 › cli codegen record › should not throw csp directive violation errors @firefox-ubuntu-22.04-node18
⚠️ [firefox-page] › page/page-wait-for-function.spec.ts:104:3 › should work with strict CSP policy @firefox-ubuntu-22.04-node18
⚠️ [chromium-library] › library/client-certificates.spec.ts:400:3 › browser › should not hang on tls errors during TLS 1.2 handshake @ubuntu-22.04-chromium-tip-of-tree
⚠️ [playwright-test] › ui-mode-test-watch.spec.ts:145:5 › should watch all @ubuntu-latest-node20-1
⚠️ [webkit-page] › page/page-screenshot.spec.ts:345:5 › page screenshot › should work while navigating @webkit-ubuntu-22.04-node18
⚠️ [playwright-test] › ui-mode-test-watch.spec.ts:145:5 › should watch all @windows-latest-node18-1

47001 passed, 983 skipped
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Merge workflow run.