Allow joins with an `and()` condition

Trying to join collections using a condition with an and() is not supported right now.

Reproduction

Adding packages/db/tests/query/join.test.ts:

type Product = {
  productId: number;
  region: 'A' | 'B' | 'C';
  sku: string;
  title: string;
}

type ProductInventory = {
  inventoryId: number;
  region: 'A' | 'B' | 'C';
  sku: string;
  quantity: number;
};

test('join with and', () => {
  const productsCollection = createCollection(
    mockSyncCollectionOptions<Product>({
      id: `test-products-join`,
      getKey: (product) => product.productId,
      initialData: [
        { productId: 1, region: 'A', sku: 'sku1', title: 'A1' },
        { productId: 2, region: 'B', sku: 'sku1', title: 'B1' },
        { productId: 3, region: 'C', sku: 'sku2', title: 'C2' },
        { productId: 4, region: 'A', sku: 'sku2', title: 'A2' },
      ],
    })
  );
  const inventoriesCollection = createCollection(
    mockSyncCollectionOptions<ProductInventory>({
      id: `test-inventories-join`,
      getKey: (inventory) => inventory.inventoryId,
      initialData: [
        { inventoryId: 1, region: 'A', sku: 'sku1', quantity: 10 },
        { inventoryId: 3, region: 'C', sku: 'sku2', quantity: 30 },
      ],
    })
  );

  const joinQuery = createLiveQueryCollection({
    startSync: true,
    query: (q) =>
      q
        .from({ product: productsCollection })
        .join(
          { inventory: inventoriesCollection },
          ({ product, inventory }) =>
            and(
              eq(product.region, product.sku),
              eq(inventory.region, inventory.sku)
            ),
        )
  });

  expect(joinQuery.toArray).toHaveLength(2);
});

And it fails with:

QueryBuilderError: Join condition must be an equality expression
 ❯ BaseQueryBuilder.join src/query/builder/index.ts:277:3
    275|   > {
    276|     return this.join(source, onCallback, `inner`)
    277|   }
       |   ^
    278|
    279|   /**
 ❯ query tests/query/join.test.ts:1459:10
 ❯ buildQuery src/query/builder/index.ts:3822:45
 ❯ buildQueryFromConfig src/query/live/collection-config-builder.ts:3737:48
 ❯ new CollectionConfigBuilder src/query/live/collection-config-builder.ts:139:9
 ❯ liveQueryCollectionOptions src/query/live-query-collection.ts:269:60
 ❯ createLiveQueryCollection src/query/live-query-collection.ts:287:46

Start with the reproduction in packages/db/tests/query/join.test.ts and inspect the join implementation at src/query/builder/index.ts:277, where the equality-expression error is raised. Run the join tests first; done means the supplied and() join case builds and returns the expected two results without the QueryBuilderError.