Wasn't being saved to flash before

Untested

A few other bits of tidying too

Also various extra tracing

Moved cyw43 git revision to top level Cargo.toml

embassy demos go back into the workspace, seems to work OK for the time
being.

Added toplevel Cargo.lock

Fixes embassy/demos/common CI

update other deps

Instead we set a flag in MethodPubkey which is the only use case for it.

Split verify() into ed25519 and rsa specific functions

This fixes PuTTY connecting. Also improve error printing

- uart is available as a "serial1" feature.
- updated to newer embassy and cyw43 with bind_interrupts
- moved picowmenu flag handlers into a separate method

Better echo handling
auth_password and auth_pubkey server behaviour methods are now async

Need to figure out echo problem

Ugly generic parameters and longer code, but it should be reusable.

A new GlobalState struct is passed around, with sessions taking a local
copy of SSHConfig.

- Can switch to usb serial mode, various other improvements to usb
  serial, can exit cleanly.
- Wifi config code written, but is unsted because it's only accessible
  by wifi...
- hostkeys() behaviour now returns a heapless::Vec

Previously it only woke when a read/write occurred.

ctrl-w and ctrl-u to erase, ctrl-c to cancel

Currently doesn't seem useful, seems like it would need more context
if it were being used.

Use READ_SIZE to size the serial read buffer that is
sent directly to ssh