dissect-image: mount the ESP with fmask=0177 (#35871)

Avoid showing the files on the ESP (i.e. a FAT formatted volume) as
executable by removing the execute permission from them.

IMO this makes the colored output of `ls` more sensible since the file
system will be mounted with `noexec` anyway.

Add a `fstype_can_fmask_dmask` function that checks if a file system
type can use the `fmask` and `dmask` mount options.

This replaces `fstype_can_umask` since it was only used in
`partition_pick_mount_options` which only cares about the file system
support for fmask & dmask now.

It somewhat reduces the coverage of the feature since there are more file
systems that support umask as opposed to those supporting dmask & dmask,
but it should not be much of an issue since fmask & dmask are supported
by vfat, exfat and ntfs3.

src/basic/mountpoint-util.c

@@ -560,13 +560,13 @@ const char* fstype_norecovery_option(const char *fstype) {
         return mount_option_supported(fstype, "norecovery", NULL) > 0 ? "norecovery" : NULL;
 }
 
-bool fstype_can_umask(const char *fstype) {
+bool fstype_can_fmask_dmask(const char *fstype) {
         assert(fstype);
 
         /* Use a curated list as first check, to avoid calling fsopen() which might load kmods, which might
          * not be allowed in our MAC context. If we don't know ourselves, on new kernels we can just ask the
          * kernel. */
-        return streq(fstype, "vfat") || mount_option_supported(fstype, "umask", "0077") > 0;
+        return streq(fstype, "vfat") || (mount_option_supported(fstype, "fmask", "0177") > 0 && mount_option_supported(fstype, "dmask", "0077") > 0);
 }
 
 bool fstype_can_uid_gid(const char *fstype) {

src/basic/mountpoint-util.h

@@ -62,7 +62,7 @@ bool fstype_is_blockdev_backed(const char *fstype);
 bool fstype_is_ro(const char *fsype);
 bool fstype_can_discard(const char *fstype);
 bool fstype_can_uid_gid(const char *fstype);
-bool fstype_can_umask(const char *fstype);
+bool fstype_can_fmask_dmask(const char *fstype);
 
 const char* fstype_norecovery_option(const char *fstype);