mkosi: Use shared extra tree between initrd and main image

Let's share more between initrd and main system and use a shared
extra tree to achieve that.

mkosi.conf

@@ -38,9 +38,8 @@ SignExpectedPcr=yes
 
 [Content]
 ExtraTrees=
+        mkosi.extra.common
         mkosi.crt:/usr/lib/verity.d/mkosi.crt # sysext verification key
-        mkosi.leak-sanitizer-suppressions:/usr/lib/systemd/leak-sanitizer-suppressions
-        mkosi.coredump-journal-storage.conf:/usr/lib/systemd/coredump.conf.d/10-coredump-journal-storage.conf
         %O/minimal-0.root-%a.raw:/usr/share/minimal_0.raw
         %O/minimal-0.root-%a-verity.raw:/usr/share/minimal_0.verity
         %O/minimal-0.root-%a-verity-sig.raw:/usr/share/minimal_0.verity.sig

mkosi.images/initrd/mkosi.conf

@@ -6,9 +6,7 @@ Include=
         %D/mkosi.sanitizers
 
 [Content]
-ExtraTrees=
-        %D/mkosi.leak-sanitizer-suppressions:/usr/lib/systemd/leak-sanitizer-suppressions
-        %D/mkosi.coredump-journal-storage.conf:/usr/lib/systemd/coredump.conf.d/10-coredump-journal-storage.conf
+ExtraTrees=%D/mkosi.extra.common
 
 Packages=
         findutils