feat: handle exec maxBuffer size with environment variable

[mproboeuf]

Provide the ability to set maxBuffer in exec command options to avoid the following error

[ERROR] VALHALLASOURCE 117 -[39m RangeError [ERR_CHILD_PROCESS_STDIO_MAXBUFFER]: stdout maxBuffer length exceeded

[azarz]

Thanks for the PR!
The only thing missing is a mention of the change in the changelog (https://github.com/IGNF/road2/blob/develop/changelog.md)
e.g.

## 2.2.7
ADDED:
- Valhalla: Provide the ability to set maxBuffer in exec command options to avoid maxBuffer lenght exceeded error

[mproboeuf]

Thanks for the PR! The only thing missing is a mention of the change in the changelog (https://github.com/IGNF/road2/blob/develop/changelog.md) e.g.

## 2.2.7
ADDED:
- Valhalla: Provide the ability to set maxBuffer in exec command options to avoid maxBuffer lenght exceeded error

Done !

[azarz]

@mproboeuf
La version taguée 2.2.7 embarque la modification, le build de l'image Docker est en cours. Une fois fini l'image sera disponible via
ghcr.io/ignf/road2:2.2.7