Add support for certain pseudo-type intersections e.g. `literal-string&non-empty-string`

[ZebulanStanphill]

PHPStan supports intersections of certain pseudo-types, which I find to be quite useful and use a lot in my projects:

• literal-string&non-empty-string (any literal string except '')
• literal-string&truthy-string (any literal string except '0' and '')
• numeric-string&truthy-string (any numeric string except '0')

Unfortunately, Psalm currently appears to only accept intersections of object types. https://psalm.dev/r/4ef9f549b4

I am aware that Psalm supports some equivalent single pseudo-types like non-empty-literal-string, and PHPStan even added support for some of these recently; but it seems counterintuitive that the intersection form wouldn't just work, and some of the IDE tooling I'm using right now in VS Code only supports the simpler pseudo-types and intersections.

[psalm-github-bot[bot]]

I found these snippets:

https://psalm.dev/r/4ef9f549b4

```php