Validate the content of the thin server-build

Follow up to WFLY-10409, but focused on server-build vs server-dist.

This is probably kind of a 3 phase thing:

1) Make sure servlet-dist is correct. Possible approach: remove modules/system and then compare the content of dist and servlet-dist, largely focusing on missing files. No need to spend energy on comparing files that exist but would reasonably differ in details, like config files, license files, .galleon dir content.

This validates servlet-dist itself.

2) Compare servlet-build to servlet-dist after removing modules/system and correct issues.

3) Look at servlet-[build|dist]-legacy which now may differ from the galleon equivalents. Adjust legacy to bring in things that were missing. Goal is to make sure we can still do diffs of galleon vs legacy to spot other issues without having to sort through too many known diffs.

This isn't particularly high priority, as it's arguable that we should drop these servlet-xxx maven modules altogether as users will be able to create equivalents using the galleon tool. Arguable, but certainly not a for sure thing.