- Introduced with the C++20 <bit> header
- The problem with __builtin_c(l|t)z() is that 0 as input has an
undefined result (*) and the code did not always check. The std::
versions do not have this issue.
- In some cases, we continue to use buildin_c(l|t)z(), (e.g. in
src/Common/BitHelpers.h) because the std:: versions only accept
unsigned inputs (and they also check that) and the casting would be
ugly.
(*) https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html
When I tried to add cool new clang-tidy 14 warnings, I noticed that the
current clang-tidy settings already produce a ton of warnings. This
commit addresses many of these. Almost all of them were non-critical,
i.e. C vs. C++ style casts.
```
Undefined symbols for architecture x86_64:
"vtable for DB::IModel", referenced from:
DB::IModel::IModel() in Obfuscator.cpp.o
NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
ld: symbol(s) not found for architecture x86_64
clang-11: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
```
The following files had some unused headers and caught my eyes, so
cleaning them up:
```bash
programs/obfuscator/Obfuscator.cpp
src/Databases/DatabaseAtomic.cpp
```
