pw_build: Require "tests" and "docs" targets in all modules

- Allow empty pw_test_group targets.
- Create empty pw_test_group targets for modules that need them.
- Create stub docs pages for modules that are missing them.
- Require odules to provide "tests" and "docs" targets by assuming
  they're present in the module list generation code.
- Update the generated modules list.

Change-Id: I5a67741afa0a8a5d2e2ba508435027f750a471c4
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/103487
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/pw_module/BUILD.gn b/pw_module/BUILD.gn
index 09696722b..45e4c14f1 100644
--- a/pw_module/BUILD.gn
+++ b/pw_module/BUILD.gn
@@ -15,7 +15,11 @@
 import("//build_overrides/pigweed.gni")
 
 import("$dir_pw_docgen/docs.gni")
+import("$dir_pw_unit_test/test.gni")
 
 pw_doc_group("docs") {
   sources = [ "docs.rst" ]
 }
+
+pw_test_group("tests") {
+}