Migrate UnlinkedParam.defaultValue to UnlinkedExecutable.bodyExpr.

pkg/analyzer/lib/src/summary/format.fbs

Index: pkg/analyzer/lib/src/summary/format.fbs
diff --git a/pkg/analyzer/lib/src/summary/format.fbs b/pkg/analyzer/lib/src/summary/format.fbs
index 92accd506b1ed15f0226bd4318b6770d63847e94..29beae08b78276989b787b59866b75f9ec8bd7fc 100644
--- a/pkg/analyzer/lib/src/summary/format.fbs
+++ b/pkg/analyzer/lib/src/summary/format.fbs
@@ -1921,14 +1921,7 @@ table UnlinkedParam {
   /**
    * Code range of the parameter.
    */
-  codeRange:CodeRange (id: 14);
-
-  /**
-   * If the parameter has a default value, the constant expression in the
-   * default value.  Note that the presence of this expression does not mean
-   * that it is a valid, check [UnlinkedConst.isInvalid].
-   */
-  defaultValue:UnlinkedConst (id: 7);
+  codeRange:CodeRange (id: 7);
 
   /**
    * If the parameter has a default value, the source text of the constant