[Enhancement]: ScriptUtils::runInitScript should load script also from local directory

Module

Core

Proposal

The ScriptUtils::runInitScript only accepts paths from the classpath. This isn't as powerful as I would have expected given:

• Absolute paths or relative paths local to the maven module, for example, are useful as well
• Being on the classpath means the Maven compile (or test-compile) phase must have run, but what if I want to use testcontainers in the generate-sources (or generate-test-sources) phase, e.g. to generate jOOQ code? In that case, the init scripts aren't available on the classpath yet, unless I create a separate module just for this, which is overkill

Additionally, there are many cases where the script doesn't have to be a file. An inline script in String form would suffice, e.g.

container.initScript("""
  create schema test;
  create table test.test (test int);
""");

Start at ScriptUtils::runInitScript and the container.initScript API mentioned in the proposal. Trace how classpath scripts are resolved, then determine how local absolute or relative paths and inline String scripts should be accepted. Done means each supported input form works, with tests covering local paths and inline SQL.