Run e2e tests using plugin-integration-testing plugin (#254)

`test/build_defs/test.build_defs` contains a vendorised, outdated
version of the `plz_e2e_test` build definition that has since been
migrated to its own plugin, please-build/plugin-integration-testing. Use
the build definition provided by the latest version of that plugin
rather than the vendorised copy.

Author: chrisnovakovic

.plzconfig

@@ -4,9 +4,6 @@ Version = >=17.12.2
 [Build]
 hashcheckers = sha256
 
-[Parse]
-PreloadBuildDefs = test/build_defs/test.build_defs
-
 [Plugin "go"]
 Target = //plugins:go
 ImportPath = github.com/please-build/python-rules
@@ -19,6 +16,9 @@ DisableVendorFlags = true
 [Plugin "shell"]
 Target = //plugins:shell
 
+[Plugin "e2e"]
+Target = //plugins:e2e
+
 [PluginDefinition]
 name = python
 

plugins/BUILD

@@ -7,3 +7,9 @@ plugin_repo(
     name = "shell",
     revision = "v0.1.2",
 )
+
+plugin_repo(
+    name = "e2e",
+    plugin = "plugin-integration-testing",
+    revision = "v1.0.3",
+)

test/BUILD

@@ -1,4 +1,8 @@
-subinclude("//build_defs:python", "///shell//build_defs:shell")
+subinclude(
+    "///e2e//build_defs:e2e",
+    "///shell//build_defs:shell",
+    "//build_defs:python",
+)
 
 package(
     default_visibility = ["PUBLIC"],