meson: simplify sdbusplus dependency

There is a lot of cruft in the sdbusplus dependency that is no longer
needed:

   1. Use "dependency" with wrap file support rather than "subproject".

   2. Remove "include_type: system" since this is part of sdbusplus
      itself now.

   3. Leverage wrap file "provides" directives for dependency variable
      lookup.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I419aed22297e004a0808d3a05f1d69abca326943
diff --git a/meson.build b/meson.build
index ef95c8f..c7e09ab 100644
--- a/meson.build
+++ b/meson.build
@@ -252,12 +252,7 @@
 endif
 bmcweb_dependencies += nghttp2
 
-sdbusplus = dependency('sdbusplus', required: false, include_type: 'system')
-if not sdbusplus.found()
-    sdbusplus_proj = subproject('sdbusplus', required: true)
-    sdbusplus = sdbusplus_proj.get_variable('sdbusplus_dep')
-    sdbusplus = sdbusplus.as_system('system')
-endif
+sdbusplus = dependency('sdbusplus')
 bmcweb_dependencies += sdbusplus
 bmcweb_cli_dependencies += sdbusplus