Clean up Environment.Frame

Make fields visibility/accessors more idiomatic. Prefer accessors that give a full map of the bindings and inherited bindings, rather than just the keys.

Also increase visibility of some accessors on Mutability.

RELNOTES: None
PiperOrigin-RevId: 155393780
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredRuleClassProvider.java b/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredRuleClassProvider.java
index 7c2b34c..7f8a72f 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredRuleClassProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredRuleClassProvider.java
@@ -762,7 +762,7 @@
       Map<String, Extension> importMap) {
     return createSkylarkRuleClassEnvironment(
         mutability,
-        globals.setLabel(extensionLabel),
+        globals.withLabel(extensionLabel),
         skylarkSemantics,
         eventHandler,
         astFileContentHashCode,