tfa-next: Enable rfa-fvp run tests in LAVA CI

The rfa-fvp setup was done to be able to run tests locally.
Add the following changes so that the runtime (not just build)
rfa-fvp tests can also run on Jenkins CI and LAVA:

 * As all tfa-next tests require the modification of the RUSTUP_HOME
   variable, modify this directly in build_package.sh before
   pre_tf_build.
 * Generate the lava job template that is later used by gen_fvp_yaml.
 * Mirror the expect/tfa-next.exp file in expect-lava as needed by
   LAVA.

Change-Id: I6fd7a36227b402111d1b93f47803deee2575eb3f
Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
5 files changed