[compiler-rt] [lld] [clang] [libc] [libclc] [lldb] [llvm] [clang-tools-extra] [flang] [libcxx] [libunwind] [clang] Add tests for DRs about complete-class context (PR #77444)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

CI fails on formatting in unrelated files, so I'm going to ignore it:
```
t=1704988008448 + echo '*** Checking for trailing whitespace left in Clang source files ***'
t=1704988008448 *** Checking for trailing whitespace left in Clang source files ***
t=1704988008448 + grep -rnI '[[:blank:]]$' clang/lib clang/include clang/docs
t=1704988008595 clang/docs/HLSL/FunctionCalls.rst:147:Clang Implementation 
t=1704988008602 + echo '*** Trailing whitespace has been found in Clang source files as described above ***'
t=1704988008602 *** Trailing whitespace has been found in Clang source files as described above ***
t=1704988008602 + exit 1
t=1704988008603 ^^^ +++
t=1704988008603 Error: The command exited with status 1
t=1704988008603 ^^^ +++
t=1704988008603 user command error: exit status 1
```
https://buildkite.com/llvm-project/github-pull-requests/builds/28418

https://github.com/llvm/llvm-project/pull/77444