Enabling extension in Dev Container does not download CodeQL CLI

首先，使用列出的 VS Code 和扩展版本，在 Linux Dev Container 中重现安装流程，然后检查扩展设置中的 CodeQL > CLI: Executable Path 以及报告的日志消息。将此行为与 issue #904 进行比较。当扩展按预期下载 CodeQL CLI，或在无法下载时清楚说明用户需要执行的操作时，即视为完成。

The underlying issue might be #904; feel free to close this issue if you think the other one covers this.

Describe the bug
When the VSCode extension is already installed (on Windows), and is then installed in a Linux Dev Container it does not download CodeQL CLI.

The CodeQL extension log shows:

Starting GitHub.vscode-codeql extension
INFO: Could not find CodeQL on path.
INFO: Could not find CodeQL on path.
INFO: Could not find CodeQL on path.
Didn't perform CodeQL CLI update check since a check was already performed within the previous 86400 seconds.
INFO: Could not find CodeQL on path.
The CodeQL CLI could not be found.

And an error dialog with the following message appears:

The CodeQL CLI could not be found.

Restarting VSCode has no effect. The same log messages appear.

Edit: Maybe this is not actually exclusive to Dev Containers and happens for a normal installation as well.

Version
CodeQL extension version: v1.5.1

VSCode:
Version: 1.57.1 (user setup)
Commit: 507ce72a4466fbb27b715c3722558bb15afa9f48
Date: 2021-06-17T13:28:07.755Z
Electron: 12.0.7
Chrome: 89.0.4389.128
Node.js: 14.16.0
V8: 8.9.255.25-electron.0
OS: Windows_NT x64 10.0.19041

To reproduce
On Windows (though maybe OS does not matter)

1. Install the CodeQL extension
2. Run >Remote-Container: Clone Repository in Named Container Volume...
3. Clone any GitHub repository, for example https://github.com/github/vscode-codeql
4. Create a new volume
5. Choose "Ubuntu" "focal" as container configuration
6. In the "Extensions" tab search for the CodeQL extension and install it for the Dev Container
   ❌ Once the installation finished it shows the error "The CodeQL CLI could not be found."

Note: Maybe step 1 can be skipped.

Apparently once you edit the extension configurations it starts downloading the CodeQL CLI:

1. Open the extension settings
2. Change "CodeQL > CLI: Executable Path" to an invalid (?) directory
   ❌ The extension shows that the executable was not found and downloads the CodeQL CLI

Maybe this is actually a separate bug? Personally I think the extension should not download the CodeQL CLI when it does not exist at the specified path; the user might have just mistyped the path. The CodeQL CLI should only be installed when the executable path is empty (which is not the case here).

Expected behavior
Ideally the extension should be able to download the CodeQL CLI on its own.
If that is, for whatever reason, not possible in a Dev Container it would be good to at least tell the user what to do.