[js/webgpu] add matmul broadcast tests (#17335)
### Description
Commit fffefb1c22a5c93d53511454bed844e9179beb0b (#16969) optimized
matmul and also fixes broadcasting. So #17191 is no longer needed.
However, the newly added operator test file from the PR by @dakenf is
helpful so pick and add it to enhance the tests.
