jq: refactor variants and fix PROVIDES

jq: refactor variants and fix PROVIDES

Refactor package variants definition to be cleaner and more robust.
E.g.:
- Remove redundant PROVIDES:=jq from the main 'jq' package (it provides
  itself automatically).
- Keep PROVIDES:=jq only on the 'jq-full' variant so it can serve as a
  drop-in replacement.
- Use $(CP) macro rather than $(INSTALL_BIN) to preserve symlinks on shared objects
INSTALL_BIN turns all of the symlinks to files, increasing size.

Fixes: 711a19c4b23f3517ece5296d323c8f0220a0ff4e ("jq: provide regex support in additional package jq-full")
Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>