[clang-tidy] Aliasing: Add more support for captures.

D96215 takes care of the situation where the variable is captured into
a nearby lambda. This patch takes care of the situation where
the current function is the lambda and the variable is one of its captures
from an enclosing scope.

The analogous problem for ^{blocks} is already handled automagically
by D96215.

Differential Revision: https://reviews.llvm.org/D101787