Revert fstatat on *nix and test symlinks in path_filestat calls (#1725)

* Revert fstatat on *nix and test symlinks in path_filestat calls

This commit effectively reverts too eager refactoring on my part which
resulted in incorrect `path_filestat_{get, set_times}` behaviour on
*nix hosts. In the presence of symlinks, neither of the calls would
work properly.

In order to shield ourselves from similar errors in the future, I've
augmented the `path_filestat` test cases with symlink checks as well.

* Pass appropriate flags to fstatat and utimensat

* Fix formatting

* Fix Windows build

* Expand final symlinks if follow is set on Windows

* Fix formatting

* Do not follow symlinks unless specified on Windows

* Update comments and restart CI

* Skip testing volatile atim field

crates/wasi-common/src/virtfs.rs

@@ -600,6 +600,36 @@ impl Handle for VirtualDir {
             }
         }
     }
+    fn filestat_get_at(&self, path: &str, _follow: bool) -> Result<types::Filestat> {
+        let stat = self
+            .openat(
+                path,
+                false,
+                false,
+                types::Oflags::empty(),
+                types::Fdflags::empty(),
+            )?
+            .filestat_get()?;
+        Ok(stat)
+    }
+    fn filestat_set_times_at(
+        &self,
+        path: &str,
+        atim: types::Timestamp,
+        mtim: types::Timestamp,
+        fst_flags: types::Fstflags,
+        _follow: bool,
+    ) -> Result<()> {
+        self.openat(
+            path,
+            false,
+            false,
+            types::Oflags::empty(),
+            types::Fdflags::empty(),
+        )?
+        .filestat_set_times(atim, mtim, fst_flags)?;
+        Ok(())
+    }
     fn openat(
         &self,
         path: &str,