Cleanup the FieldVector<K,SIZE>

This MR cleans up the FieldVector class similar to the cleanup of just the specialization FieldVector<K,1> in !1387 (merged).

The following changes are implemented

• Unify the indentation and spaces inside brackets, around brackets, and around for, if statements.
• Add constexpr to all functions where possible
• Add noexcept keyword where possible (sometimes with a condition)
• Unify the formatting of documentation comments
• Simplify the constraints on the constructors, without changing its behavior
• Cleanup of includes (remove unnecessary includes, order lexicographically, write out full path)
• Rename the include-guard to common form

This MR also contains a change discussed and implemented in !1345 (merged), which should be merged before.

assigned to @oliver.sander

added 4 commits

• abf66434...668f4e73 - 3 commits from branch master
• d48e2254 - Cleanup the FieldVector<K,SIZE>

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changed the description

Thanks! I looked at the code and didn't see anything obviously wrong. Please feel free to merge once the full CI set has passed.

I would have preferred to get the reformatting changes in a separate commit.

added 1 commit

• cfc83974 - Add explicit to deleted converting constructor

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resolved all threads

added 1 commit

• 568686d0 - Improve the documentation of FieldVector default constructor

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enabled an automatic merge when the pipeline for 568686d0 succeeds

merged

mentioned in commit 73c7034c

mentioned in merge request !1485 (merged)