Flutter Devtools create file in my $HOME and don't allow for relocation

In my home directory the following directory is created whenever I use devtools:

```
$ tree -a ~/.flutter-devtools
/Users/bartek/.flutter-devtools
└── .devtools
```

Content of that single file is:

```
$ cat ~/.flutter-devtools/.devtools
{
"analyticsEnabled": true,
"isFirstRun": false,
"lastReleaseNotesVersion": "2.31.0",
"2023-Q4": {
"surveyActionTaken": false,
"surveyShownCount": 0
}
}
```

I don't like when programs clutter my personal `~`. I very much echo sentiment of [this article](https://0x46.net/thoughts/2019/02/01/dotfile-madness). Unfortunately it looks like the location of that file is currently hardcoded ([example](https://github.com/flutter/devtools/blob/8a528c6d6575df48cdde795af82863b7b1b4d26d/packages/devtools_shared/lib/src/server/file_system.dart#L20-L23)).

Therefore I'd like for Flutter DevTools to respect [XDG Base Directory Specification](https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html), so that the `.devtools` file could be stored in (e.g.) `~/.local/state`, that is, `$XDG_STATE_HOME`.

To support migration, Flutter Devtools would continue to use `~/.flutter-devtools/.devtools` if it exists. If it does not exist, it should default to the appropriate XDG base directory.

I am willing to contribute this feature, if only the maintainers of this project agree with this suggestion.