Fix missing MAST log when there is Unicode non-decodable text in logs (#119298)
Summary:
## Issue
When there is Unicode non-decodable text in logs, `tail_logger` will stop working afterwards, i.e. f527390102
In the example, the process stopped producing Python logs after 17:20:21 untill the job finished
```
[0]:I0201 17:20:21.338000 3429 gen_ai/genie_projects/llm/metaformers/reward_model_score.py:335] Progress: 118 batches out of 512 total batches. 23.05 % | (gpu mem: 25.8GB, free CPU mem: 1387.8GB)
I0201 17:39:14 Stopping twtask-main.service with Service Result: [success] Exit Code: [exited] Exit Status: [0]
```
At the end, `UnicodeDecodeError` was thrown at the end with no call stack.
## Fix
Use `errors="replace"` to avoid throwing exception when `UnicodeDecodeError` happens.
Test Plan: f528854819
Differential Revision: D53483644
Co-authored-by: Jack Zhang <jackzh@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119298
Approved by: https://github.com/XilunWu
