[GR-7252] [GR-7314] Refactor package testing.

...oracle/truffle/r/ffi/impl/common/JavaUpCallsRFFIImpl.java

...com/oracle/truffle/r/ffi/impl/upcalls/StdUpCallsRFFI.java

...oracle.truffle.r.native/fficall/src/common/rffi_upcalls.h

...e.truffle.r.native/fficall/src/common/rffi_upcallsindex.h

...ve/fficall/src/truffle_common/Rinternals_truffle_common.h

com.oracle.truffle.r.native/version.source

...om/oracle/truffle/r/nodes/builtin/base/FileFunctions.java

com.oracle.truffle.r.test.packages/importantPackages

com.oracle.truffle.r.test.packages/r/install.cache.R

mx.fastr/mx_fastr_pkgs.py