Factored out "suppressGetenvAccess()" method

Issue: SPR-11297
Polishing

Issue: SPR-11297
Introduced SpringProperties class and optional "spring.properties" file

This in particular allows for specifying "spring.getenv.ignore" and "spring.beaninfo.ignore" in a local way within the application, in case that JVM-level system properties are locked.

Issue: SPR-9014
Issue: SPR-11297
(cherry picked from commit 8543b91)
Polishing
Allow consolidating config in root context with Java

Issue: SPR-11357
(backported from 4.0.1)
Polishing

Issue: SPR-11357
Added test for SpringProperties setFlag method

Issue: SPR-9014
Issue: SPR-11297
Optimized Introspector.flushFromCaches calls to skip Object.class

Issue: SPR-11356
Polishing

Issue: SPR-11357
Polishing