Improve UX by allowing no params for JSON-RPC requests

[marioiordanov]

Usage related changes

solves #532 devnet_dump, devnet_getPredeployedAccounts, devnet_postmanFlush take optional parameters, therefore the params property of the JSON-RPC request can be omitted. The same applies to the HTTP endpoint.

Development related changes

Fixed utility methods Added new deserialization helper for constructing Optional types during deserialization

Checklist:

• [ ] Checked out the contribution guidelines
• [ ] Applied formatting - ./scripts/format.sh
• [ ] No linter errors - ./scripts/clippy_check.sh
• [ ] No unused dependencies - ./scripts/check_unused_deps.sh
• [ ] No spelling errors - ./scripts/check_spelling.sh
• [ ] Performed code self-review
• [ ] Rebased to the latest commit of the target branch (or merged it into my branch)
  • Once you make the PR reviewable, please prefer merging over rebasing
• [ ] Updated the docs if needed - ./website/README.md
• [ ] Linked the issues resolvable by this PR - linking info
• [ ] Updated the tests if needed; all passing - execution info