Show pop-up when analysis is finished and found some new reports

[csordasmarton]

CodeChecker analysis can be slow (1-2 minutes). It would be good if we could show a pop-up window to inform the user when the analysis finished. We can show this pop-up window only when we found new results.

Also if started to analyze a file and the analysis is still in progress we can add a decoration to the analyzed file by using FileDecorations:

Example code to provide file decorations

```ts export class CodeCheckerFileDecorationProvider implements FileDecorationProvider { constructor(ctx: ExtensionContext) { ctx.subscriptions.push(window.registerFileDecorationProvider(this)); } provideFileDecoration(uri: Uri, token: CancellationToken) { return new FileDecoration("CC", "CodeChecker analysis in progress", new ThemeColor('progressBar.background')); } } ```

[vodorok]

Displaying reports will be significantly sped up by implementing this feature in CodeChecker: https://github.com/Ericsson/codechecker/issues/3759