Update to rustix 0.26.2. (#3521)

This pulls in a fix for Android, where Android's seccomp policy on older
versions is to make `openat2` irrecoverably crash the process, so we have
to do a version check up front rather than relying on `ENOSYS` to
determine if `openat2` is supported.

And it pulls in the fix for the link errors when multiple versions of
rsix/rustix are linked in.

And it has updates for two crate renamings: rsix has been renamed to
rustix, and unsafe-io has been renamed to io-extras.

tests/all/custom_signal_handler.rs

@@ -4,7 +4,7 @@
 ))]
 mod tests {
     use anyhow::Result;
-    use rsix::io::{mprotect, MprotectFlags};
+    use rustix::io::{mprotect, MprotectFlags};
     use std::sync::atomic::{AtomicBool, Ordering};
     use std::sync::Arc;
     use wasmtime::unix::StoreExt;