Refine the logic introduced in 64270eca to use a side-effect free
Environment implementation rather than converting the Environment early.
Early conversion can cause condition evaluation issues if
`src/test/resources/application.properties` files are bound to the
`SpringApplication`. Specifically the `spring.main.web-application-type`
property can change the `Environment` type which must happen before
conditions are evaluated.
Fixes gh-29169
eb6b48fff0