chore: abort pending operations upon disconnect

[dgozman]

This involves a few changes:

• protocol cleanup as every channel is now "progress: true";
• keeping ProgressController instances of ongoing operations inside the dispatcher;
• replacing Dispatcher._openScope with aborting progress controllers;
• instead of issuing stopPendingOperations() when disconnecting from a reused context, we call an explicit disconnectFromReusedContext() method;
• various small cleanups.

References #35987.

[github-actions]

Test results for "tests 1"

1 failed
❌ [playwright-test] › reporter-html.spec.ts:2924:5 › merged › execSync doesnt produce a second stdout attachment @macos-latest-node18-2

3 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
⚠️ [playwright-test] › ui-mode-test-watch.spec.ts:145:5 › should watch all @ubuntu-latest-node18-1

47010 passed, 983 skipped
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Merge workflow run.