CodeQL CLI update dialog blocks extension start / update dialog is easy to miss

從 extensions/ql-vscode/src/extension.ts 的第 207-208 行附近開始，然後透過等待 CodeQL CLI 發行版本或操弄 VS Code 全域儲存空間來重現更新條件。確認被忽略的更新對話框如何影響擴充功能動作，並將完成標準定義為允許擴充功能啟動，同時仍適當地顯示更新通知。

Describe the bug
Relates to #297, #447

When a CodeQL CLI update is available the start of the extension is blocked until the user interacted with the update dialog, see:
https://github.com/github/vscode-codeql/blob/db66184c35410bc2545a9d9a1d37305c8b99c2e6/extensions/ql-vscode/src/extension.ts#L207-L208

However, personally I think the info dialog shown by VSCode is easy to miss, especially when there are other dialogs from other extensions (and VSCode collapses the CodeQL dialog?).
When you then overlook CodeQL's dialog, you will wonder why the extension is not working.

Version
Extension:

CodeQL extension version: 1.5.1 
CodeQL CLI version: 2.5.7 
Platform: win32 x64

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

1. Wait for the next CodeQL CLI release (maybe also possible with VSCode global storage manipulation)
2. Start VSCode with the extension installed
3. Activate the extension, for example by clicking on the "CodeQL" icon on the left sidebar
   ℹ️ The extension should show an info dialog about the CodeQL CLI update in the bottom right corner
4. Ignore the update dialog (neither close it nor accept it)
5. Try to use any extension action
   ❌ Nothing happens (note: from my memories; cannot test because there is no new CodeQL CLI release)

Expected behavior
Maybe the dialog should not be blocking and the extension should start with the existing CodeQL CLI?