fix: fix JCEF browser issues

[exigow]

Solves CON-2469
Solves CON-2979
Solves #5504

Changes

Off-screen rendering is the new default

Off-screen rendering is now enabled by default. This is motivated by the fact that most users will benefit from it,
but the minority with issues can disable it in the Continue settings. I believe this is the correct strategy,
because disabling it causes a flickering window for the majority.

Note: I tried to mask it by preloading the HTML with a background color and by changing the background color of the
browser component. That worked, but only reduced the flashing time and didn't completely eliminate the problem.
Enabling Off-screen rendering seems to be the only robust solution.

Fix JS_QUERY_POOL_SIZE errors

After decoupling the browser from the toolbar and moving it to a dedicated service, there is now full control over
when and what is initialized. The setting is now applied correctly.

Rework actions

I've noticed that most of the actions require a working, active Continue toolbar.
I've created the ContinueToolbarAction abstraction to remove duplicated logic. I've also removed actions.utils.

Minor changes

• Fix bug in CoreMessenger.handleMessage (some pass-through messages had message type used as message ID)
• Add browser package and moved browser-related classes there, including CustomHandlerFactory (package factories is now removed). CustomHandlerFactory implementation is untouched.
• Add project.getBrowser() extension method (this is mostly for readability).
• Some loggers now use a shorter identifier (simple class name) without the full package, because our package name is
  unusually long, and it was hard to read the logs.
• Remove commented-out TerminalActivityTrackingService.
• Create JcefErrorPanel and put jcef_error.html there.

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[exigow]

I tested all the features (actions, focusing, chat functionalities) and it seems to be OK, except for one action that doesn’t recognize the command focusContinueInputWithoutClear, however, this issue existed before. I squashed all the "wip" commits into a single one with all the details.

[exigow]

I'm switching it back to draft because we need to discuss OSR (let's wait with merge).

[exigow]

✅ TODO: Remove OSR from settings (it should be enabled by default with no option to change).

I've enabled OSR by default and removed the option. I also made sure there are no outdated comments in the readme/contribute docs.

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[Patrick-Erichsen]

@exigow I think the test failure here is no longer flake. Might be a test that we can just remove though, lmk your thoughts.

[exigow]

@Patrick-Erichsen, you're right, it was failing test (compilation error caused by changes in our browser code). 😅

I think it's better to remove it. The test was fine, but almost everything was mocked there and the test was heavily dependent on the handler's code (+ everything around). It made some sense, but ideally there should be as few mocks as possible and it should be tested in a more black-box manner.

If you think we should keep it, let me know - I'll try to fix it.

[exigow]

Interesting error on CI (it's from e2e test I suppose):

[0826/175633.869512:FATAL:setuid_sandbox_host.cc(158)] The SUID sandbox helper binary was found, but is not configured correctly. Rather than run without sandboxing I'm aborting now. You need to make sure that /home/runner/.gradle/caches/8.14.3/transforms/83a0ed050b837f55f39183dd9bb4af55/transformed/ideaIC-2024.1/jbr/lib/chrome-sandbox is owned by root and has mode 4755.

Test is passing locally. 😮‍💨 I'm investigating this right now.

[exigow]

🟢

(fix: 2b085c1)