Add `gates.GeneralizedRBS` gate

[renatomello]

This needs https://github.com/qiboteam/qibojit/pull/183

Checklist:

• [x] Reviewers confirm new code works as expected.
• [x] Tests are passing.
• [x] Coverage does not decrease.
• [x] Documentation is updated.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.94%. Comparing base (37e1010) to head (3e83876). Report is 46 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1373 +/- ## ======================================= Coverage 99.94% 99.94% ======================================= Files 78 78 Lines 11236 11297 +61 ======================================= + Hits 11230 11291 +61 Misses 6 6 ``` | [Flag](https://app.codecov.io/gh/qiboteam/qibo/pull/1373/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/qiboteam/qibo/pull/1373/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | `99.94% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[renatomello]

@scarrazza @MatteoRobbiati the PR in qibojit needs to be merged before this one