grpc: fix installed CMake package

grpc: fix installed CMake package

The CMake package configuration installed by grpc ends up not being
usable in practice.  Add a bbappend that adds the fixes:
- a do_install:append to correct the version number to the actual
  version, as it gets mangled somehow during the grpc build.  This
  is required to avoid triggering version mismatch checks when using
  the package in CMake.
- backport a fix from the kirkstone branch of meta-openembedded that
  splits the host tools (i.e. protoc plugins) out into a separate
  CMake package.  This avoids failures due to CMake not playing well
  with the split native versus target sysroots that OpenEmbedded
  uses.  This may be revisited if grpc upstream comes up with a
  different approach.

Bug-AGL: SPEC-4405

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: Ia284901c148c1fcdf1b8ab77947d8be9445be631