When there's a huge file, escapeStreamer.Text will be very slow

### Description

When there's a huge file, escapeStreamer.Text will be very slow.

### Gitea Version

103b94f96

### Can you reproduce the bug on the Gitea demo site?

Yes

### Log Gist

_No response_

### Screenshots

_No response_

### Git Version

_No response_

### Operating System

_No response_

### How are you running Gitea?

Run ./gitea on linux.

### Database

MySQL