Don't use umask when calculating new file permissions inherited from a default ACL

### Description

Linux skips the umask step when inheriting perms from an ACL, doing so in gVisor will require relatively major changes since umask isn't passed along to VFS at all, instead masked into the mode directly at the syscall layer.

### Is this feature related to a specific bug?

_No response_

### Do you have a specific solution in mind?

_No response_

Start by tracing how the syscall layer masks the mode with umask before it reaches VFS, then examine how VFS handles permissions inherited from a default ACL. Compare this flow with Linux behavior; done means default-ACL inheritance no longer applies umask while other permission handling remains correct.

Written by the indexing model from the issue text.