Start Adding GitHub Actions (#1165)

Summary:
This change starts adding more coverage to GitHub Actions. Existing workflows are split up to be per-platform, and stale scripts, etc are removed.

We are currently limited a bit by issues with the build itself, but this still adds a good bit of coverage that readily works, and adds places to inject more.

Another option would have been to move these to CircleCI where we have more credits, or used docker images instead of manual setup steps. etc, The Yoga build and number of changes is very light though, so we don't really need the complexity yet.

Some TODOs:
1. Fix the Apple Builds (pod lint and pod install return errors seen by the community)
2. Add working Android UTs
3. Add C++ UTs
4. Add Apple Publish
5. Add version stamping

Changelog:
[Internal][Added] - Start Adding Yoga GitHub Actions

Pull Request resolved: https://github.com/facebook/yoga/pull/1165

Reviewed By: cortinico

Differential Revision: D40386426

Pulled By: NickGerleman

fbshipit-source-id: c540dd25bfec6ac8c05e461c1236ef7fe6cb8598

enums.py

@@ -72,10 +72,10 @@ def get_license(ext):
  * LICENSE file in the root directory of this source tree.
  */
 
-// @generated by enums.py
+// @{} by enums.py
 
 """.format(
-        prologue
+        prologue, "generated"
     )
 
 
@@ -107,13 +107,13 @@ root = os.path.dirname(os.path.abspath(__file__))
 with open(root + "/yoga/YGEnums.h", "w") as f:
     f.write(get_license("cpp"))
     f.write("#pragma once\n")
-    f.write("// clang-format: off\n\n")
     f.write('#include "YGMacros.h"\n\n')
+    f.write("// clang-format off\n\n\n")
 
-    f.write('YG_EXTERN_C_BEGIN\n\n')
+    f.write("YG_EXTERN_C_BEGIN\n\n")
     items = sorted(ENUMS.items())
     for name, values in items:
-        if (isinstance(values[0], tuple)):
+        if isinstance(values[0], tuple):
             f.write("YG_ENUM_DECL(\n")
         else:
             f.write("YG_ENUM_SEQ_DECL(\n")