SMB3 Directory Leases

From WHATSNEW.txt:

SMB3 Directory Leases

Starting with Samba 4.22 SMB3 Directory Leases will be supported. The new global option "smb3 directory leases" controls whether the feature is enabled or not. By default, SMB3 Directory Leases are enabled on non-clustered Samba and disabled on clustered Samba, based on the "clustering" option.

SMB3 Directory Leases allow clients to cache directory listings and, depending on the workload, result in a decent reduction in SMB requests from clients.

This MR depends on !3797 (closed).

Fwiw, this also passes the Directory Leases tests in MS-Protocol-Testsuite.