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