Make globs work in remote repositories.

This involved quite a few changes, mainly changing a bunch of places where we refer to packages by a PathFragment to PackageIdentifier. 

The only wart is the code in PathPackageLocator: ideally, it would just call into PackageLookupFunction. Unfortunately, it is (through globbing and Parser.include) called from within a Skyframe function, and we don't want to have two eval() calls going on at the same time, so we cannot use that.

There is a potential correctness issue there: PathPackageLocator now assumes where external repositories are put and assumes that they are there when it gets control, but my understanding is that the associated RepositoryValue is always evaluated before, so it works out okay.

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MOS_MIGRATED_REVID=97751539
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/EnvironmentBackedRecursivePackageProvider.java b/src/main/java/com/google/devtools/build/lib/skyframe/EnvironmentBackedRecursivePackageProvider.java
index 9ea6210..ac5b6a2 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/EnvironmentBackedRecursivePackageProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/EnvironmentBackedRecursivePackageProvider.java
@@ -64,9 +64,9 @@
   }
 
   @Override
-  public boolean isPackage(EventHandler eventHandler, String packageName)
+  public boolean isPackage(EventHandler eventHandler, PackageIdentifier packageId)
       throws MissingDepException {
-    SkyKey packageLookupKey = PackageLookupValue.key(new PathFragment(packageName));
+    SkyKey packageLookupKey = PackageLookupValue.key(packageId);
     try {
       PackageLookupValue packageLookupValue =
           (PackageLookupValue) env.getValueOrThrow(packageLookupKey, NoSuchPackageException.class,