Introduce BlazeInterners, a Blaze-specific wrapper around Guava's Interners that makes an appropriate call to Interners.InternerBuilder#concurrencyLevel.

For current readers of this CL, I used this class everywhere in the Blaze codebase.

For future readers of this CL, this class should be used to create an Interner in the Blaze codebase.

--
MOS_MIGRATED_REVID=140063271
diff --git a/src/main/java/com/google/devtools/build/skyframe/IntVersion.java b/src/main/java/com/google/devtools/build/skyframe/IntVersion.java
index 68a2cfa..3f3761a 100644
--- a/src/main/java/com/google/devtools/build/skyframe/IntVersion.java
+++ b/src/main/java/com/google/devtools/build/skyframe/IntVersion.java
@@ -14,11 +14,11 @@
 package com.google.devtools.build.skyframe;
 
 import com.google.common.collect.Interner;
-import com.google.common.collect.Interners;
+import com.google.devtools.build.lib.concurrent.BlazeInterners;
 
 /** Versioning scheme based on integers. */
 final class IntVersion implements Version {
-  private static final Interner<IntVersion> interner = Interners.newWeakInterner();
+  private static final Interner<IntVersion> interner = BlazeInterners.newWeakInterner();
 
   private final long val;