Check that deprecation replacement property exists in additional-spring-configuration-metadata.json

[mhalbritter]

It's possible to specify a non-existent property in the "deprecation"."replacement" field. I think it should be possible to validate that the referenced property exists.

[wilkinsona]

This might be tricky on main when the replacement may be in a different module but should be easier in the 3.x branches.

[snicoll]

This could happen at the spring-boot-docs level when we generate the appendix or something? Even in 3.x, I don't think we should validate the replacement with a partial view of the world.