Previously, the initialization of StandardServletEnvironment's
property sources in SpringBootServletInitializer led to debug logging
calls being made before the LoggingSystem had been initialized. As a
result, the system's default configuration was used and, in the case
of Logback at least, the debug logging was output to System.out
in a war deployment.

This commit updates SpringBootServletInitializer to delay the
initialization of StandardServletEnvironment's property sources until
after the LoggingSystem has been initialized, but still in time for
active profiles to be configured via servlet context parameters
(see gh-9972).

Closes gh-13736