refactor!: shorter constructors, bucket → subtable (#22)

## Description

Currently, the name of `bucket` is a bit confusing, because it is considered a 'table' in literature (as well as the whole hash table). A `bucket` is better described as a 'subtable', which is used by the total hash table to perform cuckoo hashing.

In addition, the constructors `NewTable`, `NewTableBy`, and `NewCustomTable` were given shorter names, because the package name `cuckoo` already implies that `New*` would create a hash table with cuckoo hashing. This package has one use-case, and so it unambiguous what constructors produce.

## Changes

- `NewTable` -> `New`
- `NewTableBy` -> `NewBy`
- `NewCustomTable` -> `NewCustom`
- `bucket` -> `subtable`

### Design Decisions

- I would have renamed `Table` and `subtable` to map equivalents, but 'submap' implies that a certain subsection of the map is contained within it, which isn't quite right.
- I chose not to go with `Map` and `table`, because of the split naming convention.

## Checklist

- [x] Tests pass
- [x] Docs updated

Reviewed-on: #22
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

cuckoo_internal_test.go

@@ -11,7 +11,7 @@ func TestMaxEvictions(t *testing.T) {
 	assert := assert.New(t)
 
 	for i := 16; i < 116; i++ {
-		table := NewTable[int, bool](Capacity(i / 2))
+		table := New[int, bool](Capacity(i / 2))
 		expectedEvictions := 3 * math.Floor(math.Log2(float64(i)))
 
 		assert.Equal(table.maxEvictions(), int(expectedEvictions))
@@ -20,7 +20,7 @@ func TestMaxEvictions(t *testing.T) {
 
 func TestLoad(t *testing.T) {
 	assert := assert.New(t)
-	table := NewTable[int, bool](Capacity(8))
+	table := New[int, bool](Capacity(8))
 
 	for i := range 16 {
 		err := table.Put(i, true)