This is a follow-up to 119afdf788f4fec0eaae0def91a95aee84971eae Since
continue/fulfill/abort now may throw on the server after page has been
closed, we need to catch the errors manually. On the client it's fixed
by the original change.
This fixes errors in the existing tests:
```
1) [chromium] › library/browsercontext-route.spec.ts:172:3 › should support Set-Cookie header ────
Error:
at ../packages/playwright-core/src/server/chromium/crConnection.ts:147
145 | const id = this._connection._rawSend(this._sessionId, method, params);
146 | return new Promise((resolve, reject) => {
> 147 | this._callbacks.set(id, { resolve, reject, error: new ProtocolError('error', method) });
| ^
148 | });
149 | }
150 |
at /Users/yurys/playwright/packages/playwright-core/src/server/chromium/crConnection.ts:147:57
at new Promise (<anonymous>)
at CRSession.send (/Users/yurys/playwright/packages/playwright-core/src/server/chromium/crConnection.ts:146:12)
at RouteImpl.continue (/Users/yurys/playwright/packages/playwright-core/src/server/chromium/crNetworkManager.ts:566:25)
at FrameManager.requestStarted (/Users/yurys/playwright/packages/playwright-core/src/server/frames.ts:299:23)
at CRNetworkManager._onRequest (/Users/yurys/playwright/packages/playwright-core/src/server/chromium/crNetworkManager.ts:314:57)
at CRNetworkManager._onRequestPaused (/Users/yurys/playwright/packages/playwright-core/src/server/chromium/crNetworkManager.ts:202:12)
at CRSession.emit (node:events:517:28)
at /Users/yurys/playwright/packages/playwright-core/src/server/chromium/crConnection.ts:172:14
at runNextTicks (node:internal/process/task_queues:60:5)
at processImmediate (node:internal/timers:447:9)
```

Reference https://github.com/microsoft/playwright/issues/28490
This patch:
- changes the `childProcess` fixture to reliably SIGKILL all descendants
(children and grand-children, regardless of their process group).
This is achieved using the `ps` command to build the process tree, and
then send
`SIGKILL` to the descendant process groups.
- changes the `runCLI` fixture to **not** auto-close codegen by default;
the `childProcess` fixture will clean up all processes. This makes
sure that all `runCLI.waitFor()` commands actually wait until the
necessary
output.
- for a handful of tests that do actually want to auto-close codegen,
introduce an optional `autoCloseWhen` flag for the `runCLI` fixture
that makes sure to close the codegen once a certain output was reached.
- Rename internal selectors `has`, `control` and `attr` to
`internal:has`, `internal:control` and `internal:attr`.
- Fix `getByLabel()` to respect strictness, by introducing
`internal:label` selector.
- Move tests essential for ports to `selectors-by.spec`.