Stop returning NOTCAPABLE errors from WASI calls. (#4666)

* Stop returning `NOTCAPABLE` errors from WASI calls.

`ENOTCAPABLE` was an error code that is used as part of the rights
system, from CloudABI. There is a set of flags associated with each file
descriptor listing which operations can be performed with the file
descriptor, and if an attempt is made to perform an operation with a
file descriptor that isn't permitted by its rights flags, it fails with
`ENOTCAPABLE`.

WASI is removing the rights system. For example, WebAssembly/wasi-libc#294
removed support for translating `ENOTCAPABLE` into POSIX error codes, on
the assumption that engines should stop using it.

So as another step to migrating away from the rights system, remove uses
of the `ENOTCAPABLE` error.

* Update crates/wasi-common/src/file.rs

Co-authored-by: Jamey Sharp <jamey@minilop.net>

* Update crates/wasi-common/src/dir.rs

Co-authored-by: Jamey Sharp <jamey@minilop.net>

Co-authored-by: Jamey Sharp <jamey@minilop.net>

crates/wasi-common/src/error.rs

@@ -72,6 +72,9 @@ pub enum ErrorKind {
     /// Errno::Spipe: Invalid seek
     #[error("Spipe: Invalid seek")]
     Spipe,
+    /// Errno::Perm: Permission denied
+    #[error("Permission denied")]
+    Perm,
     /// Errno::NotCapable: Not capable
     #[error("Not capable")]
     NotCapable,
@@ -92,7 +95,7 @@ pub trait ErrorExt {
     fn overflow() -> Self;
     fn range() -> Self;
     fn seek_pipe() -> Self;
-    fn not_capable() -> Self;
+    fn perm() -> Self;
 }
 
 impl ErrorExt for Error {
@@ -138,7 +141,7 @@ impl ErrorExt for Error {
     fn seek_pipe() -> Self {
         ErrorKind::Spipe.into()
     }
-    fn not_capable() -> Self {
-        ErrorKind::NotCapable.into()
+    fn perm() -> Self {
+        ErrorKind::Perm.into()
     }
 }