refactor: make use of anyDuplicated and map_* pattern

[m-muecke]

• Replace any(duplicated(x)) with anyDuplicated(x)
• Replace unlist(map(...)) with map_*(...)
• Replace map with walk if used for side effects
• Remove fda package from suggests since its currently only used in attic dir
• Make use of lengths(x)
• Make use of testthat::expect_named(...)

[codecov-commenter]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (ab8a88d) 69.07% compared to head (857e029) 68.89%.

:exclamation: Current head 857e029 differs from pull request most recent head 535a929. Consider uploading reports for the commit 535a929 to get more accurate results

Files	Patch %	Lines
R/print-format.R	0.00%	4 Missing :warning:
R/vctrs.R	84.61%	2 Missing :warning:
R/methods.R	0.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #67 +/- ## ========================================== - Coverage 69.07% 68.89% -0.18% ========================================== Files 26 26 Lines 1636 1630 -6 ========================================== - Hits 1130 1123 -7 - Misses 506 507 +1 ```

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[fabian-s]

dankeschööön