Addition of linear algebra `operations` submodule to `quantum_info` module

[renatomello]

Checklist:

• [ ] 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 99.84%. Comparing base (c68e58b) to head (2296946).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1372 +/- ## ======================================= Coverage 99.84% 99.84% ======================================= Files 74 75 +1 Lines 10791 10809 +18 ======================================= + Hits 10774 10792 +18 Misses 17 17 ``` | [Flag](https://app.codecov.io/gh/qiboteam/qibo/pull/1372/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/1372/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | `99.84% <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.