Add expression for generic_name in csharp-ts-mode (bug#59897)

Add expression for generic_name in csharp-ts-mode (bug#59897)

Given the below example, we want 'services' to be font-locked in
'font-lock-variable-name-face' in all cases.  Previously this only
worked in the first case, and the other was font-locked as
'font-lock-function-name-face'.

namespace Foo {
    void Foo() {
        services.Add();
        services.Add<MyType>();
    }
}

* lisp/progmodes/csharp-mode.el (csharp-ts-mode--font-lock-settings):
Add new query that makes the mentioned example work.