build: add vpp-opt-deps package

- Build an optional vpp package for optional
  dynamically linked dependencies for vpp plugins.
  Initial package contents include openssl 3.3.2.
- Refactor $WS_ROOT/build makefile structure
- Remove vpp-ext-deps debian control replacement
  of vpp-dpdk-dev package

Type: make

Change-Id: I1af0eff4a0c009c9d9061362f79e2013d8bf1a93
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>

.gitignore

@@ -31,6 +31,17 @@
 /build/external/deb/debian/files/
 /build/external/deb/debian/.debhelper/
 /build/external/deb/debian/vpp-ext-deps*
+/build/optional/downloads/
+/build/optional/*.tar.gz
+/build/optional/*.tar.xz
+/build/optional/vpp-*
+/build/optional/deb/_build/
+/build/optional/deb/debian/changelog
+/build/optional/deb/debian/debhelper-build-stamp
+/build/optional/deb/debian/tmp/
+/build/optional/deb/debian/files/
+/build/optional/deb/debian/.debhelper/
+/build/optional/deb/debian/vpp-ext-deps*
 /path_setup
 /tools/
 # start autotools ignore