Convert expressions from standard to TextFirst

[anderson-joyle]

We need to convert standard expressions into TextFirst format. Possibly TexlNode.ToTextFirstString().

Examples: Input: "ordinary text" Output: ordinary text

Input: $"3 {3+3}" Output: 3 ${3+3}

[MikeStall]

These are both text first and mean the same thing as $"3 {3+3}": =$"3 {3+3}"

Same as: 3 ${3+3}