Add missing package-info files for common packages

Issue: SPR-14420
(cherry picked from commit 66ec1c1)

spring-expression/src/main/java/org/springframework/expression/common/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Common utility classes behind the <em>Spring Expression Language</em>.
+ */
+package org.springframework.expression.common;

spring-expression/src/main/java/org/springframework/expression/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * Core abstractions behind the <em>Spring Expression Language</em>.
+ */
+package org.springframework.expression;

spring-expression/src/main/java/org/springframework/expression/spel/ast/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * SpEL's abstract syntax tree.
+ */
+package org.springframework.expression.spel.ast;

spring-expression/src/main/java/org/springframework/expression/spel/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * SpEL's central implementation package.
+ */
+package org.springframework.expression.spel;

spring-expression/src/main/java/org/springframework/expression/spel/standard/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * SpEL's standard parser implementation.
+ */
+package org.springframework.expression.spel.standard;

spring-expression/src/main/java/org/springframework/expression/spel/support/package-info.java

@@ -0,0 +1,4 @@
+/**
+ * SpEL's default implementations for various core abstractions.
+ */
+package org.springframework.expression.spel.support;