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>

Makefile

@@ -271,6 +271,7 @@ help:
 	@echo " snap-clean           - clean up snap build environment"
 	@echo " pkg-rpm              - build RPM packages"
 	@echo " install-ext-dep[s]   - install external development dependencies"
+	@echo " install-opt-deps     - install optional dependencies"
 	@echo " ctags                - (re)generate ctags database"
 	@echo " gtags                - (re)generate gtags database"
 	@echo " cscope               - (re)generate cscope database"
@@ -740,6 +741,10 @@ install-ext-deps:
 .PHONY: install-ext-dep
 install-ext-dep: install-ext-deps
 
+.PHONY: install-opt-deps
+install-opt-deps:
+	$(MAKE) -C build/optional install-$(PKG)
+
 .PHONY: json-api-files
 json-api-files:
 	$(WS_ROOT)/src/tools/vppapigen/generate_json.py