[MISC] Refactor STL views

[eseiler]

• [x] Change pragma once to include guards
• [x] Use seqan4::std::viewable_range
• [x] Use workaround for nested class friend access

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Name	Status	Preview	Comments	Updated (UTC)
seqan3	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 15, 2023 9:08am

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: -0.08 :warning:

Comparison is base (f371f87) 98.20% compared to head (a8ab9f4) 98.13%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3149 +/- ## ========================================== - Coverage 98.20% 98.13% -0.08% ========================================== Files 276 269 -7 Lines 12281 11817 -464 ========================================== - Hits 12061 11597 -464 Misses 220 220 ``` [see 3 files with indirect coverage changes](https://app.codecov.io/gh/seqan/seqan3/pull/3149/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=seqan)

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