[InlineCost] Fix infinite loop in indirect call evaluation

Currently every time we encounter an indirect call of a known function,
we try to evaluate the inline cost of that function. In case of a
recursion, that evaluation never stops.

The solution I propose is to evaluate only the indirect call of the
function, while any further indirect calls (of a known function) will be
treated just as direct function calls, which, actually, never tries to
evaluate the call.

Fixes PR35469.

Differential Revision: https://reviews.llvm.org/D69349