feat: add drop key functionality (#6)

Currently, the `Table.Drop()` function is deprecated because it is not implemented yet. Let's add that functionality.

- Adds true drop functionality to the table, through `Table.Drop()`.
- Adds tests for functionality.
- Rewrites fuzz test using `go_fuzz_utils`, to test arbitrary usage patterns.
- Rewrite `bucket` to allow a capacity of zero.
- Rename `Table.Capacity()` to `Table.TotalCapacity()`, to reflect to different between the capacity of the buckets vs. the whole table.
- Enforce 100% mutation test coverage.

Reviewed-on: #6
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

bucket.go

@@ -17,15 +17,37 @@ type bucket[K, V any] struct {
 	compare        EqualFunc[K]
 }
 
+// location determines where in the bucket a certain key would be placed. If the
+// capacity is 0, this will panic.
 func (b bucket[K, V]) location(key K) uint64 {
 	return b.hash(key) % b.capacity
 }
 
 func (b bucket[K, V]) get(key K) (value V, found bool) {
+	if b.capacity == 0 {
+		return
+	}
+
 	slot := b.slots[b.location(key)]
 	return slot.value, slot.occupied && b.compare(slot.key, key)
 }
 
+func (b *bucket[K, V]) drop(key K) (occupied bool) {
+	if b.capacity == 0 {
+		return
+	}
+
+	slot := &b.slots[b.location(key)]
+
+	if slot.occupied && b.compare(slot.key, key) {
+		slot.occupied = false
+		b.size--
+		return true
+	}
+
+	return false
+}
+
 func (b *bucket[K, V]) resize(capacity uint64) {
 	b.slots = make([]slot[K, V], capacity)
 	b.capacity = capacity
@@ -33,6 +55,10 @@ func (b *bucket[K, V]) resize(capacity uint64) {
 }
 
 func (b bucket[K, V]) update(key K, value V) (updated bool) {
+	if b.capacity == 0 {
+		return
+	}
+
 	slot := &b.slots[b.location(key)]
 
 	if slot.occupied && b.compare(slot.key, key) {
@@ -44,6 +70,10 @@ func (b bucket[K, V]) update(key K, value V) (updated bool) {
 }
 
 func (b *bucket[K, V]) evict(insertion entry[K, V]) (evicted entry[K, V], eviction bool) {
+	if b.capacity == 0 {
+		return insertion, true
+	}
+
 	slot := &b.slots[b.location(insertion.key)]
 
 	if !slot.occupied {