getSolutionFile silently selects the first solution when multiple are found

[BinToss]

Describe the bug

async function getSolutionFile(): Promise<string | undefined> {
	const filePattern = "**/*.sln";
	const files = await vscode.workspace.findFiles(filePattern);

	if (files.length > 0) {
		return files[0].fsPath;
	}

	return vscode.workspace.workspaceFolders?.[0].uri.fsPath;
}

This function may automatically select the "incorrect" solution file when multiple are found in the workspace.
Now, the user is given the choice of which solution file we read.

I've committed a fix, but I still need to create a separate branch and open a PR.

To Reproduce

Avalonia for VS Code

v0.0.17-v0.0.29

Avalonia version

No response

VS Code version

No response

Relevant log output

> irrelevant

Additional context

No response