[llvm] Change how branch weight is annotated for direct call (PR #90315)

[Lei Wang via llvm-commits]

wlei-llvm wrote:

>  if the profile is a product of merging/downsampling multiple profiles.

is this due to stale profile? I can think of a scenario that two profiles are from different versions.
in one version:
```
main:100:50
 1: 50 DirectCallee: 50
 2: 50
```
say another version add one line at the beginning of main. Then 
```
main:100:50
 1: 50
 2: 50 DirectCallee: 50
 3: 50
```
merging them will get:
```
main:200:100
 1: 100 DirectCallee: 50
 2: 100 DirectCallee: 50
 3: 50
```
Though either way may not be perfect in this case. 

https://github.com/llvm/llvm-project/pull/90315