[chain_redesign] Remove old structures

Other changes:

* The `async-https` feature of `bdk_esplora` is no longer default.
* Rename `ObservedAs` to `ChainPosition`.
* Set temporary MSRV to 1.60.0 to compile all workspace members will all
  features.

crates/esplora/src/lib.rs

@@ -1,9 +1,8 @@
 #![doc = include_str!("../README.md")]
-use bdk_chain::{BlockId, ConfirmationTime, ConfirmationTimeAnchor};
+use bdk_chain::{BlockId, ConfirmationTimeAnchor};
 use esplora_client::TxStatus;
 
 pub use esplora_client;
-pub mod v2;
 
 #[cfg(feature = "blocking")]
 mod blocking_ext;
@@ -15,18 +14,6 @@ mod async_ext;
 #[cfg(feature = "async")]
 pub use async_ext::*;
 
-pub(crate) fn map_confirmation_time(
-    tx_status: &TxStatus,
-    height_at_start: u32,
-) -> ConfirmationTime {
-    match (tx_status.block_time, tx_status.block_height) {
-        (Some(time), Some(height)) if height <= height_at_start => {
-            ConfirmationTime::Confirmed { height, time }
-        }
-        _ => ConfirmationTime::Unconfirmed { last_seen: 0 },
-    }
-}
-
 pub(crate) fn map_confirmation_time_anchor(
     tx_status: &TxStatus,
     tip_at_start: BlockId,