[lldb] add a marker before hidden frames (#167550)

**This patch adds a marker to make hidden frames more explicit.**

---

Hidden frames can be confusing for some users, who see that the indexes
of the frames in a backtrace are not contiguous. This patch aims to
lessen the confusion by adding a delimiter for the first and last non
hidden frame, i.e the boundaries.

IDE's like Xcode and VSCode represent those in the UI by having the
hidden frames either greyed out or collapsed.

It's not possible to do this in the CLI, therefore, this patch makes use
of 2 unicode characters to mark the beginning and end of the hidden
frames range.

This patch depends on:
- https://github.com/llvm/llvm-project/pull/168603

# Examples

In the example below, frame `#2` to `#7` are is hidden, and therefore,
frame `#1` is the first non hidden frame of the range while frame `#8`
is the last non hidden frame:
<img width="488" height="112" alt="Screenshot 2025-11-18 at 18 41 11"
src="https://github.com/user-attachments/assets/a21431da-9729-4cf0-a6bc-024aa306fc45"
/>

If the selected frame is one of the 2 boundary frames, we replace the
delimiter character with the select character (`*`).

<img width="487" height="111" alt="Screenshot 2025-11-18 at 18 41 03"
src="https://github.com/user-attachments/assets/5616fa81-6db6-457d-9d1e-bbe46e710c26"
/>
<img width="488" height="111" alt="Screenshot 2025-11-18 at 18 40 55"
src="https://github.com/user-attachments/assets/93dfa6cf-0956-4718-b31c-f965ec72b56d"
/>
GitOrigin-RevId: e43331f94a594421180ee783b5b92e5dea70f4c9