Merge #3307

3307: test: open IntegrationTestRpc and add comment r=zhangsoledad a=chanhsu001

### What problem does this PR solve?

Open IntegrationTestRpc in rpc/module/test, add rpc comment document.

### What is changed and how it works?

- open 6 functions,  add check Dummy PoW chain in integration test (not add separate check in each function) 
- add encoding_rs license.clarify in deny.toml( reqwest crate refer to encoding_rs)

### Check List

Tests <!-- At least one of them must be included. -->

- No code ci-runs-only: [ quick_checks,linters ]


### Release note <!-- Choose from None, Title Only and Note. Bugfixes or new features need a release note. -->

```release-note
None: Exclude this PR from release note.
```

Co-authored-by: chanhsu001 <chanhsu001@cryptape.com>

Author: bors[bot]