[TRACKING] Support launching Maxima from Epic/Steam

[imLinguin]

Why

The implementation found in EA App itself doesn't support launching those games when offline, it seems to always want to go through the login gate with given storefront's parameters to get new EA credentials. While this is fine when online (different account could be linked or something), offline workload is not supported at all.

Steps

• Implement link2ea protocol handling
• Implement origin2 protocol handling

Needs further discussion

An interesting use-case would be to have Steam client for Linux be able to call native Maxima instead of EA App installed in the wine prefix. That way we could get make running EA games a lot more stable experience on Linux, without risking EA App would break when it gets updated. How could this be approached, custom compatibility layer? Integration with GE-Proton + env variable?

[imLinguin]

The proposed solution discussed on Discord, dependent on #23
The protocol handler will:

• Be responsible for initialization and proxying of an appropriate SDK depending on the platform thats used.
• Communicate with Maxima server instance to start an appropriate game session.

Linux challenges:

• Should Maxima server be woken up on-demand? Maybe by relying on D-Bus? - can be done with flatpaks
• The protocol handler may have to be ran in the same prefix and be responsible for launch of the game executable - this may require ability to handle external connections - Don't reject external LSX connections #42

Additional things that we could do:

• Request game launch of given titles when started from Maxima.

Proposed flow of EA game installed from Steam through Proton on Linux:

• ProtonGE or other supported one, prompted by an environment variable switch will call Maxima's own handler with link2ea protocol
• Handler will proceed to initialize steam_api for that game and get its install location.
• Handler will use unixlib to call a dbus interface exposed by maxima-service in order to ensure it's running
• That location then will be used to get parameters necessary to start the game. Maxima Service at this point should prepare the OOA license in game's prefix.
• Protocol handler should then use the obtained parameters to launch the game process