[clang-tidy] Rewrite modernize-avoid-bind check.

This represents largely a full re-write of modernize-avoid-bind, adding
significant new functionality in the process. In particular:

* Both boost::bind and std::bind are now supported
* Function objects are supported in addition to functions
* Member functions are supported
* Nested calls are supported using capture-init syntax
* std::ref() and boost::ref() are now recognized, and will capture by reference.
* Rather than capturing with a global =, we now build up an individual
  capture list that is both necessary and sufficient for the call.
* Fixits are supported in a much larger variety of scenarios than before.

All previous tests pass under the re-write, but a large number of new
tests have been added as well.

Differential Revision: https://reviews.llvm.org/D70368