* add `isNamedTuple`; make $(1, 2) be (1, 2) instead of leaking implementation detail (Field0: 1, Field1: 2)
fixes this: #8670 (comment) /cc @alehander42 @Vindaar @mratsim
* Note: isNamedTuple is useful in other places, eg #10010 (comment)
* move isNamedTuple to helpers.nim to avoid exposing new symbol to system.nim
* remove workaround in tests/vm/tissues.nim failing test now that #10218 was makes it work
During the instantiation of a generic type A, some other generic
type B may be instantiated multiple times with different parameters.
We can think about each instantiation as a function call that should
temporary bind the parameter names to concrete types. The problem
with the existing implementation in semtypinst was that it was
performing this binding within a shared global table. In this sense,
it was executing the code as a programming language featuring only
global variables. In such a language, re-entrant functions cannot be
defined properly and hence this was leading to problems with similar
types. The solution is simple - just like we need to introduce stack
frames to handle re-entrant functions, we introduce a stack of type
bindings that are pushed and popped during the generic instantiations.
