refactor joins to use direct implementation or each type rather than composition of inner+anti joins

.changeset/fast-joins-redesign.md

@@ -0,0 +1,5 @@
+---
+"@tanstack/db-ivm": patch
+---
+
+Redesign of the join operators with direct algorithms for major performance improvements by replacing composition-based joins (inner+anti) with implementation using mass tracking. Delivers significant performance gains while maintaining full correctness for all join types (inner, left, right, full, anti).

packages/db-ivm/src/multiset.ts

@@ -209,6 +209,12 @@ export class MultiSet<T> {
     chunkedArrayPush(this.#inner, otherArray)
   }
 
+  add(item: T, multiplicity: number): void {
+    if (multiplicity !== 0) {
+      this.#inner.push([item, multiplicity])
+    }
+  }
+
   getInner(): MultiSetArray<T> {
     return this.#inner
   }