Install + package remsim-apitool as separate sub-package

As the script depends on python3, let's put it into a new
osmo-remsim-apitool package.

As we're installing the tool system-wide, rename it from
remsim-apitool.py to osmo-remsim-apitool.

Closes: OS#5612
Change-Id: I11d779f66833b5294ffeb422ce6b2a705719a899
diff --git a/contrib/Makefile.am b/contrib/Makefile.am
index 17f56ed..a172ab3 100644
--- a/contrib/Makefile.am
+++ b/contrib/Makefile.am
@@ -1,3 +1,5 @@
 SUBDIRS = etc_default systemd
 
-EXTRA_DIST = remsim-apitool.py owhw-event-script.sh
+EXTRA_DIST = osmo-remsim-apitool owhw-event-script.sh
+
+bin_SCRIPTS = osmo-remsim-apitool