refactor: use assignment operator, use leading zero, one call to format_bib

[m-muecke]

@fabian-s have a look when its convenient, most the changes are already reflected in the package, i.e. mainly consistency changes

• Use a single call to format_bib()
• Use leading zero
• Use assignment operator
• Minor formatting
• Remove escaping of characters where not needed
• Use expect_named() instead of expect_equal(names(...))
• Use scalar logical operators
• Use length.out instead l in seq() calls
• Remove redundant return (e.g. at the end of a function)
• Remove redundant else statement after return/stop calls
• Use anonymous functions instead of formula syntax

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 72.91667% with 26 lines in your changes missing coverage. Please review.

Project coverage is 74.06%. Comparing base (f5a2eec) to head (dd3ea69). Report is 16 commits behind head on dev.

:exclamation: Current head dd3ea69 differs from pull request most recent head 75679ab

Please upload reports for the commit 75679ab to get more accurate results.

Files	Patch %	Lines
R/rebase.R	22.22%	7 Missing :warning:
R/ops.R	73.33%	4 Missing :warning:
R/soft-impute-svd.R	63.63%	4 Missing :warning:
R/methods.R	0.00%	3 Missing :warning:
R/fwise.R	80.00%	2 Missing :warning:
R/summarize.R	84.61%	2 Missing :warning:
R/utils.R	66.66%	2 Missing :warning:
R/tfd-class.R	66.66%	1 Missing :warning:
R/vctrs-ptype2.R	83.33%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #92 +/- ## ========================================== - Coverage 74.36% 74.06% -0.30% ========================================== Files 28 28 Lines 1771 1770 -1 ========================================== - Hits 1317 1311 -6 - Misses 454 459 +5 ```

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[fabian-s]

nice! thank you :)