[trivial] fix style nitpicks
[Refactoring] Improve error check in CallExp::semantic
[Refactoring] ParamXXX::fp
[stash] todo sc?
Improve overloadApply for integrated function/template overloads
Use overloadApply for template overload set iteration

Remove `TemplateOverloadSet` type
Add OverDeclaration

Recognize it in overloadApply.
fix Issue 10658 - Cannot merge template overload set by using alias declaration

- Use OverDeclaration for template overload set merging
- Check OverDeclaration in DotVarExp and VarExp