Remove usages of boost::starts/ends_with

Per the coding standard, now that C++ supports std::string::starts_with
and std::string::ends_with, we should be using them over the boost
alternatives.  This commit goes through and updates all usages.

Arguably some of these are incorrect, and instances of common error 13,
but because this is mostly a mechanical it intentionally doesn't try to
handle it.

Tested: Unit tests pass.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ic4c6e5d0da90f7442693199dc691a47d2240fa4f