Merge #5497

5497: Store macro invocation parameters as text instead of tt r=jonas-schievink a=lnicola

We don't want to expand macros on every source change because it can be arbitrarily slow, but the token trees can be rather large. So instead we can cache the invocation parameters (as text).

Co-authored-by: Laurențiu Nicola <lnicola@dend.ro>