Consider to change RelativePattern ctor argument order

re #34831

Maybe it's me but it feels weird to have a relative pattern that puts the pattern before the base. While the reading goes *"pattern 'relative to' base"*, the mental model goes like *"base + pattern"*

```ts
new vscode.RelativePattern('*.ts', folder);
```

vs

```ts
// closer to how I would manually write a pattern
new vscode.RelativePattern(folder, '*.ts');
```