[clang-format] Correctly annotate operator free function call

[clang-format] Correctly annotate operator free function call

The annotator correctly annotates an overloaded operator call when
called as a member function, like `x.operator+(y)`, however, when called
as a free function, like `operator+(x, y)`, the annotator assumed it was
an overloaded operator function *declaration*, instead of a call.

This patch allows for a free function call to correctly be annotated as
a call, but only if the current like cannot be a declaration, usually
within the bodies of a function.

Fixes https://github.com/llvm/llvm-project/issues/49973

Reviewed By: HazardyKnusperkeks, owenpan, MyDeveloperDay, Nuullll

Differential Revision: https://reviews.llvm.org/D153798