[lldb][Breakpoint] Fix setting breakpoints on templates by basename

This patch fixes a regression with setting breakpoints on template
functions by name. E.g.,:
```
$ cat main.cpp
template<typename T>
struct Foo {
  template<typename U>
  void func() {}
};

int main() {
  Foo<int> f;
  f.func<double>();
}

(lldb) br se -n func
```

This has regressed since `3339000e`
where we started using the `CPlusPlusNameParser` for getting the
basename of the function symbol and match it exactly against
the name in the breakpoint command. The parser will include template
parameters in the basename, so the exact match will always fail

**Testing**

* Added API tests
* Added unit-tests

Differential Revision: https://reviews.llvm.org/D135921