Update default signals to match agl-vcar definition

Update default signals to match agl-vcar definition

Changes:
- Updated the generated examples/agl-vcar/agl-vcar-signals.cpp and
  plugins/default-signals.cpp files with versions generated from
  examples/agl-vcar/signals.json with an updated version of
  low-level-can-generator.
- Removed plugins/agl-vcar-signals.cpp to avoid confusion, as it is
  not used.
- Removed unnecessary execute permission on plugins/CMakeLists.txt.

Bug-AGL: SPEC-3603

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I33ccecf7b1316e8735a7f362c965cb927ed147b4