This pr fixes#167388 .
## Description
This pr adds new method `GetArchName` to `SBTarget` so that no need to
parse triple to get arch name in client code.
## Testing
### All from `TestTargetAPI.py`
run test with
```
./build/bin/lldb-dotest -v -p TestTargetAPI.py
```
<details>
<summary>existing tests (without newly added)</summary>
<img width="1425" height="804" alt="image"
src="https://github.com/user-attachments/assets/617e4c69-5c6b-44c4-9aeb-b751a47e253c"
/>
</details>
<details>
<summary>existing tests (with newly added)</summary>
<img width="1422" height="778" alt="image"
src="https://github.com/user-attachments/assets/746990a1-df88-4348-a090-224963d3c640"
/>
</details>
### Only `test_get_arch_name`
run test with
```
./build/bin/lldb-dotest -v -p TestTargetAPI.py -f test_get_arch_name_dwarf -f test_get_arch_name_dwo -f test_get_arch_name_dsym lldb/test/API/python_api/target
```
<details>
<summary>only newly added</summary>
<img width="1422" height="778" alt="image"
src="https://github.com/user-attachments/assets/fcaafa5d-2622-4171-acee-e104ecee0652"
/>
</details>
---------
Signed-off-by: Nikita B <n2h9z4@gmail.com>
Co-authored-by: Jonas Devlieghere <jonas@devlieghere.com>
a4d42775b9