Remove conditionals from epoch_from_block_number

Upon analyzing the conditional logic of the `epoch_from_block_height`
it seems that we really want the epoch to increase on the successor of
the multiples of the `epoch_height`.  The conditional branches make this less obvious with 3 separate computed results for the calculation.  It seems that this can be achieved with a single statement.

In addition, extra clarity as to the parameter's intents can be added by
renaming `epoch_height` to something that indicates what the
parameter is symbolizing.

crates/types/src/utils.rs

@@ -241,15 +241,15 @@ pub fn bincode_opts() -> WithOtherTrailing<
 }
 
 /// Returns an epoch number given a block number and an epoch height
+///
+/// The epoch has the following properties:
+/// - `block_number` 0 is always epoch 0
+/// - `block_number` 1 is the first block in epoch 1
+/// - The epoch increases every `blocks_per_epoch`
+/// - Every epoch, other than 0, has `blocks_per_epoch` blocks within it
 #[must_use]
-pub fn epoch_from_block_number(block_number: u64, epoch_height: u64) -> u64 {
-    if epoch_height == 0 {
-        0
-    } else if block_number % epoch_height == 0 {
-        block_number / epoch_height
-    } else {
-        block_number / epoch_height + 1
-    }
+pub fn epoch_from_block_number(block_number: u64, blocks_per_epoch: u64) -> u64 {
+    (block_number + blocks_per_epoch - 1) / blocks_per_epoch
 }
 
 /// A function for generating a cute little user mnemonic from a hash