tests,shell: enable some shell tests on Windows

In this commit:
- split //src/test/shell:shell_utils_test into a
  symlink-specific part and the rest
- use the Bash runfiles library
- add "windows_tests" and "all_windows_tests"
  targets as we do in other platforms (e.g. in
  //src:BUILD)

See https://github.com/bazelbuild/bazel/issues/4930
See https://github.com/bazelbuild/bazel/issues/4292

Change-Id: I111a7fed223f1f9b767dc6411389465f8da3e043
PiperOrigin-RevId: 194395011
diff --git a/src/BUILD b/src/BUILD
index c539dd6..8f5da4f 100644
--- a/src/BUILD
+++ b/src/BUILD
@@ -387,8 +387,7 @@
         "//src/test/java/com/google/devtools/common/options:all_windows_tests",
         "//src/test/native:all_windows_tests",
         "//src/test/py/bazel:all_windows_tests",
-        "//src/test/shell/bazel:bazel_bootstrap_distfile_test",
-        "//src/test/shell/bazel:bazel_windows_example_test",
+        "//src/test/shell:all_windows_tests",
         "//src/tools/launcher:all_windows_tests",
         "//src/tools/runfiles:all_windows_tests",
         "//third_party/def_parser:all_windows_tests",