test: add random tree operation tests

[weiihann]

This PR adds a random tree operation test case, referring Geth's TestRandom implementation. Minor modifications are as follows:

• only 32 bytes of random keys are created
• omitting opItercheckhash and opNodeDiff, can add them once the functionalities are ready

[jsign]

Thank you!

Left some comments for your consideration.

If you can please take a look at the CI lints, there're a couple of things to fix that are quite easy. You can run the linter locally by running go run github.com/golangci/golangci-lint/cmd/golangci-lint@v1.54.2 run if helps.

After the changes I can re-review again to approve.