Support multi-line comments in SQL scripts

Prior to this commit neither ResourceDatabasePopulator nor
JdbcTestUtils properly supported multi-line comments (e.g., /* ... */).
Secondarily there has developed a significant amount of code
duplication in these two classes that has led to maintenance issues
over the years.

This commit addresses these issues as follows:

 - Common code has been extracted from ResourceDatabasePopulator and
   JdbcTestUtils and moved to a new ScriptUtils class in the
   spring-jdbc module.

 - Relevant test cases have been migrated from JdbcTestUtilsTests to
   ScriptUtilsTests.

 - ScriptUtils.splitSqlScript() has been modified to ignore multi-line
   comments in scripts during processing.

 - ResourceDatabasePopulator supports configuration of the start and end
   delimiters for multi-line (block) comments.

 - A new test case was added to ScriptUtilsTests for the new multi-line
   comment support.

Issue: SPR-9531

spring-test/src/test/resources/org/springframework/test/jdbc/test-data-with-comments-and-leading-tabs.sql

@@ -1,9 +0,0 @@
--- The next comment line starts with a tab.
-	-- x, y, z...
-
-insert into customer (id, name)
-values	(1, 'Sam Brannen');
-	-- This is also a comment with a leading tab.
-insert into orders(id, order_date, customer_id) values (1, '2013-06-08', 1);
-	 	-- This is also a comment with a leading tab, a space, and a tab.
-insert into orders(id, order_date, customer_id) values (2, '2013-06-08', 1);

spring-test/src/test/resources/org/springframework/test/jdbc/test-data-with-comments.sql

@@ -1,16 +0,0 @@
--- The next comment line has no text after the '--' prefix.
---
--- The next comment line starts with a space.
- -- x, y, z...
-
-insert into customer (id, name)
-values	(1, 'Rod; Johnson'), (2, 'Adrian Collier');
--- This is also a comment.
-insert into orders(id, order_date, customer_id)
-values (1, '2008-01-02', 2);
-insert into orders(id, order_date, customer_id) values (1, '2008-01-02', 2);
-INSERT INTO persons( person_id--      
-                   , name)
-VALUES( 1      -- person_id
-      , 'Name' --name
-);--