[DOC] Remove argument parser tutorial in favour of sharg.

[smehringer]

~Blocked by #3107~

This basically removes the seqan3::argument_parser tutorial with all its snippets and instead refers to sharg for argument parsing. To make things easier for the user, I also added a quick "How to add sharg next to seqan3" on the page.

[vercel[bot]]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated
seqan3	✅ Ready (Inspect)	Visit Preview	Dec 7, 2022 at 11:35AM (UTC)

[codecov[bot]]

Codecov Report

Base: 98.22% // Head: 98.22% // No change to project coverage :thumbsup:

Coverage data is based on head (80bcc8e) compared to base (cdff3dd). Patch coverage: 100.00% of modified lines in pull request are covered.

:exclamation: Current head 80bcc8e differs from pull request most recent head 611f581. Consider uploading reports for the commit 611f581 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3108 +/- ## ======================================= Coverage 98.22% 98.22% ======================================= Files 275 275 Lines 12192 12192 ======================================= Hits 11975 11975 Misses 217 217 ``` | [Impacted Files](https://codecov.io/gh/seqan/seqan3/pull/3108?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=seqan) | Coverage Δ | | |---|---|---| | [include/seqan3/argument\_parser/argument\_parser.hpp](https://codecov.io/gh/seqan/seqan3/pull/3108/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=seqan#diff-aW5jbHVkZS9zZXFhbjMvYXJndW1lbnRfcGFyc2VyL2FyZ3VtZW50X3BhcnNlci5ocHA=) | `97.48% <ø> (ø)` | | | [include/seqan3/argument\_parser/validators.hpp](https://codecov.io/gh/seqan/seqan3/pull/3108/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=seqan#diff-aW5jbHVkZS9zZXFhbjMvYXJndW1lbnRfcGFyc2VyL3ZhbGlkYXRvcnMuaHBw) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=seqan). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=seqan)

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.