Feature Request: Don't print stack trace to Serial on crash

### Basic Infos

- [x] This issue complies with the [issue POLICY doc](https://github.com/esp8266/Arduino/blob/master/POLICY.md).
- [x] I have read the documentation at [readthedocs](https://arduino-esp8266.readthedocs.io/en/latest) and the issue is not addressed there.
- [x] I have tested that the issue is present in current master branch (aka latest git).
- [x] I have searched the issue tracker for a similar issue.
- [N/A] If there is a stack dump, I have decoded it.
- [x] I have filled out all fields below.

#### Platform

- Hardware: ESP8266
- Core Version: 3.1.2 (latest)
- Development Env: VS Code + Microsoft Arduino Extension
- Operating System: Windows

### Settings in IDE

- Module: Generic ESP8266 Module

### Problem Description

Hi there, I'm trying to change the behavior of the `postmortem_report()` call not to print anything to the Serial upon a crash. The serial port in question is connected to a peripherical and is not used for debugging purposes.

So far, my efforts in #9193 have been unsuccessful. I am unable to override the `postmortem_report()` call via my code.

This got me thinking, can you possibly please introduce a new flag that would prevent the default function from being defined, or avoid printing to the serial? Currently the `custom_crash_callback()` callback is called _after_ the `postmortem_report()` has finished printing to the Serial port.

The addition of this would be awesome.

Thank you for the project!