Look over clang-format indentation with many specifiers

[kronbichler]

In #8428 we observed that clang-format does sometimes struggle with creating a good indentation when we use many specifiers, sometimes hidden behind the keywords. The result can look e.g.

static constexpr DEAL_II_ALWAYS_INLINE DEAL_II_CUDA_HOST_DEV T
                                                             value(const F &f,
                                                                   typename std::enable_if<

This looks ugly and sometimes even breaks the 80 char line length (as here).

Before the next release we should look this through systematically and find out whether

• an update of clang-format to a newer version would help
• there are some settings in clang-format that arrange items in a better way
• we can manually fix a few of the most offending lines as proposed by @tjhei in Enforce inlining in simple tensor functions #8428 (comment)

[kronbichler]

This is not critical and likely nobody is really interested in working on this now, so I'm adjusting the target milestone.

[masterleinad]

Let's do #11108 after the release.

[kronbichler]

#11108 has been done and it overall looks better, closing.