Declare our module dep on failureaccess as [transitive](https://dev.java/learn/modules/implied-readability/), and improve module deps in testlib, too.

See #2970 (comment)

RELNOTES=Modified the `guava` module's dependency on `failureaccess` to be `transitive`. Also, modified the `guava-testlib` module to make its dependency on `guava` transitive, to remove its dependency on `failureaccess`, and to add a dependency (`transitive`) on `junit`.
PiperOrigin-RevId: 742835889

Author: cpovirk

guava-testlib/src/module-info.java

@@ -15,8 +15,8 @@
 /** Guava Testlib */
 module com.google.common.testlib {
   requires java.logging;
-  requires com.google.common;
-  requires com.google.common.util.concurrent.internal;
+  requires transitive com.google.common;
+  requires transitive junit;
   requires static com.google.errorprone.annotations;
   requires static com.google.j2objc.annotations;
   requires static org.jspecify;

guava/src/module-info.java

@@ -17,7 +17,7 @@
 /** Google Guava */
 module com.google.common {
   requires java.logging;
-  requires com.google.common.util.concurrent.internal;
+  requires transitive com.google.common.util.concurrent.internal;
   requires static jdk.unsupported;
   requires static com.google.errorprone.annotations;
   requires static com.google.j2objc.annotations;