Remove FeePriority::Default

Done in consultation with @j-berman.

The RPC/CLI/GUI almost always adjust up except barring very explicit commands,
hence why FeePriority 0 is now only exposed via the explicit command of
FeePriority::Custom { priority: 0 }.

Also helps with terminology.

coins/monero/src/wallet/send/mod.rs

@@ -270,7 +270,6 @@ impl Fee {
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
 #[allow(non_camel_case_types)]
 pub enum FeePriority {
-  Default,
   Unimportant,
   Normal,
   Elevated,
@@ -283,7 +282,6 @@ pub enum FeePriority {
 impl FeePriority {
   pub(crate) fn fee_priority(&self) -> u32 {
     match self {
-      FeePriority::Default => 0,
       FeePriority::Unimportant => 1,
       FeePriority::Normal => 2,
       FeePriority::Elevated => 3,

coins/monero/tests/wallet2_compatibility.rs

@@ -90,8 +90,6 @@ async fn from_wallet_rpc_to_self(spec: AddressSpec) {
 
   // TODO: Needs https://github.com/monero-project/monero/pull/8882
   // let fee_rate = daemon_rpc
-  //   // Uses `FeePriority::Unimportant` instead of `FeePriority::Default` because wallet RPC
-  //   // adjusts `monero_rpc::TransferPriority::Default` up by 1
   //   .get_fee(daemon_rpc.get_protocol().await.unwrap(), FeePriority::Unimportant)
   //   .await
   //   .unwrap();