Make Target copy-able

Clippy also informed us that we can drop some of the clone calls.

```
❯ cargo clippy
    Checking veilid-core v0.2.5 (~/Developer/veilid/veilid-core)
error: using `clone` on type `Target` which implements the `Copy` trait
   --> veilid-core/src/storage_manager/record_store.rs:912:33
    |
912 |                         target: w.target.clone(),
    |                                 ^^^^^^^^^^^^^^^^ help: try removing the `clone` call: `w.target`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_copy
note: the lint level is defined here
   --> veilid-core/src/lib.rs:25:9
    |
25  | #![deny(clippy::all)]
    |         ^^^^^^^^^^^
    = note: `#[deny(clippy::clone_on_copy)]` implied by `#[deny(clippy::all)]`

error: using `clone` on type `Target` which implements the `Copy` trait
   --> veilid-core/src/storage_manager/watch_value.rs:199:21
    |
199 |                     target.clone(),
    |                     ^^^^^^^^^^^^^^ help: try removing the `clone` call: `target`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_copy

error: using `clone` on type `Target` which implements the `Copy` trait
   --> veilid-core/src/storage_manager/mod.rs:737:17
    |
737 |                 vc.target.clone(),
    |                 ^^^^^^^^^^^^^^^^^ help: try removing the `clone` call: `vc.target`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_copy

error: could not compile `veilid-core` (lib) due to 3 previous errors
```

veilid-core/src/storage_manager/mod.rs

@@ -734,7 +734,7 @@ impl StorageManager {
 
         let dest = rpc_processor
             .resolve_target_to_destination(
-                vc.target.clone(),
+                vc.target,
                 SafetySelection::Unsafe(Sequencing::NoPreference),
             )
             .await

veilid-core/src/storage_manager/record_store.rs

@@ -909,7 +909,7 @@ where
                     }
 
                     evcis.push(EarlyValueChangedInfo {
-                        target: w.target.clone(),
+                        target: w.target,
                         key: rtk.key,
                         subkeys,
                         count,

veilid-core/src/storage_manager/watch_value.rs

@@ -196,7 +196,7 @@ impl StorageManager {
                     subkeys.clone(),
                     expiration,
                     count,
-                    target.clone(),
+                    target,
                     watcher,
                 )
                 .await?;

veilid-core/src/veilid_api/routing_context.rs

@@ -3,7 +3,7 @@ use super::*;
 ///////////////////////////////////////////////////////////////////////////////////////
 
 /// Valid destinations for a message sent over a routing context
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq, Hash, Copy, PartialOrd, Ord)]
 pub enum Target {
     /// Node by its public key
     NodeId(TypedKey),