Remove PrintCompressedOopsMode and change gc+heap+coops info log to debug level

After JDK-8244817 the basic compressed oops information is printed with gc+init on info level. The the more detailed gc+heap+coops log can therefor be moved to debug level to avoid the somewhat duplicated logs in the -Xlog:gc* case.

When changing this it also makes sense to clean out an old alias flag for compressed oops logging: PrintCompressedOopsMode