Move GetAuxvData from Host to relevant process plugins

Summary:
GetAuxvData was causing dependencies from host to target and linux
process modules. It also does not fit netbsd use case, as there we can
only read the auxiliary vector with ptrace, which is better done in the
process plugin, with the other ptrace calls.

I resolve these issues by moving the freebsd and linux versions into the
relevant process plugins. In case of linux, this required adding an
interface in NativeProcessProtocol. The empty definitions on other
platforms can simply be removed.

To get the code compiling I had to add ProcessGdbRemote -> ProcessLinux
dependency, which was not caught before because we depended on it
transitively.

Reviewers: zturner, emaste

Subscribers: srhines, mgorny, lldb-commits

Differential Revision: https://reviews.llvm.org/D31031

llvm-svn: 298066