[clang-tools-extra] [clang-tidy] Add new check readability-trailing-comma (PR #173669)

[via cfe-commits]

https://github.com/zeyi2 commented:

Personally, I agree with localspook's idea about multiple line checking.

e.g. Code that looks like this are very common
```c
int foo[] = {1, 2, 3};
```

but after this check, it may be transformed to:
```c
int foo[] = {1, 2, 3,};
```
I think the fix adds visual noise.

---

Also, (at first glance) multi line detection will not introduce a lot of new code, we can just check if `SM.getExpansionLineNumber(InitList->getBeginLoc())` and `SM.getExpansionLineNumber(InitList->getEndLoc())` gives the same value :)

https://github.com/llvm/llvm-project/pull/173669