Return more info from HT insert/update methods

[pelijah]

Your checklist for this pull request

• [ ] I've read the guidelines for contributing to this repository
• [ ] I made sure to follow the project's coding style
• [X] I've documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• [X] I've added tests that prove my fix is effective or that my feature works (if possible)
• [ ] I've updated the rizin book with the relevant information (if needed)

Detailed description

HT insert/update methods don't provide information about what really happened: was KV inserted/updated or existing KV prevented insertion. In result it requires to do extra requests to a HT.