Use session scope in qgis_bot fixture

[Joonalai]

This PR:

• Turns qgis_bot into session scoped fixture since its only requirement is session scoped as well and it has no reason to have any other scope
• Deprecates module_qgis_bot since it has no purpose anymore

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (631d92b) 56.35% compared to head (b856341) 56.44%.

Files	Patch %	Lines
src/pytest_qgis/pytest_qgis.py	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #46 +/- ## ========================================== + Coverage 56.35% 56.44% +0.08% ========================================== Files 7 7 Lines 488 489 +1 ========================================== + Hits 275 276 +1 Misses 213 213 ``` | [Flag](https://app.codecov.io/gh/GispoCoding/pytest-qgis/pull/46/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GispoCoding) | Coverage Δ | | |---|---|---| | [pytest](https://app.codecov.io/gh/GispoCoding/pytest-qgis/pull/46/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GispoCoding) | `56.44% <50.00%> (+0.08%)` | :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=GispoCoding#carryforward-flags-in-the-pull-request-comment) to find out more.

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