Move docker build stuff into a subdirectory. Update structure to retire manual-{pre,post}

docker/files/etc/vpp/startup.conf

@@ -0,0 +1,50 @@
+# This is the vpp-containerlab default startup.conf, which is meant to be
+# overridden by Containerlab's node/fdio_vpp/vpp_startup_config.go.tpl
+
+unix {
+  interactive
+  log /var/log/vpp/vpp.log
+  full-coredump
+  cli-listen /run/vpp/cli.sock
+  cli-prompt vpp-clab#
+  cli-no-pager
+  poll-sleep-usec 100
+  exec /etc/vpp/bootstrap.vpp
+}
+
+api-trace {
+  on
+}
+
+memory {
+  main-heap-size 512M
+  main-heap-page-size 4k
+}
+
+buffers {
+  buffers-per-numa 16000
+  default data-size 2048
+  page-size 4k
+}
+
+statseg {
+  size 64M
+  page-size 4k
+  per-node-counters on
+}
+
+plugins {
+  plugin default { enable }
+  plugin dpdk_plugin.so { disable }
+  plugin linux_cp_plugin.so { enable }
+  plugin linux_nl_plugin.so { enable }
+  plugin sflow_plugin.so { enable }
+}
+
+linux-cp {
+  default netns dataplane
+  lcp-sync
+  lcp-auto-subint
+  del-static-on-link-down
+  del-dynamic-on-link-down
+}