Support comments in SQL scripts in JdbcTestUtils

Prior to this commit, utility methods in JdbcTestUtils interpreted SQL
comments as separate statements, resulting in an exception when such a
script is executed.

This commit addresses this issue by introducing a
readScript(lineNumberReader, String) method that accepts a comment
prefix. Comment lines are therefore no longer returned in the parsed
script. Furthermore, the existing readScript(lineNumberReader) method
now delegates to this new readScript() method, supplying "--" as the
default comment prefix.

Issue: SPR-9593

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

@@ -0,0 +1,6 @@
+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);