mia, desktop-ui: Add basic error handling to ROM loading

[jcm93]

Note

Seeking testers on this to validate that errors appear correctly, are accurate, and we didn't break anything.

Description

Adds the LoadResult type, used to identify and propagate upwards errors encountered when loading ROMs and systems.

Modifies the mia and desktop-ui load routines to use this type instead of generic booleans, so that if we have a load failure, we can propagate a precise and useful error to the user rather than a vague and possibly mismatched one.

Currently the scope of the error handling is just mia and desktop-ui; errors encountered when loading in ares itself are currently generic "otherError"s. LoadResult is placed in mia/mia.hpp so it is accessible to both mia and desktop-ui. If LoadResult is added to ares loading in the future, the LoadResult type may need to be moved.

[LukeUsher]

Since most of these errors are regarding ROM loading and manifest parsing; which mia is responsible for creating/handling; I believe these error types would be better suited as part of mia.hpp.

[LukeUsher]

Just a few notes

[jcm93]

Taking this out of draft now that it's in a better state.

ares/mia/medium/arcade.cpp

Line 12 in 90860c2

if(!manifest) return romNotFoundInDatabase;

I am still not 100% on if this is correct/representative of the underlying behavior. Arcade seems to be the only system with an existing failure condition here. It seems like it's bailing out if the game entry wasn't in the database rather than using heuristics like the other cores. Just want to make sure this is accurate. And if so, maybe a more descriptive error message is appropriate? "The selected [game/Arcade system] is not currently supported by ares"?

[LukeUsher]

Taking this out of draft now that it's in a better state.

ares/mia/medium/arcade.cpp

Line 12 in 90860c2

if(!manifest) return romNotFoundInDatabase;

I am still not 100% on if this is correct/representative of the underlying behavior. Arcade seems to be the only system with an existing failure condition here. It seems like it's bailing out if the game entry wasn't in the database rather than using heuristics like the other cores. Just want to make sure this is accurate. And if so, maybe a more descriptive error message is appropriate? "The selected [game/Arcade system] is not currently supported by ares"?

This is indeed correct; due to how arcade roms are formatted, ares does not know how to load them without a database entry specifying which individual roms need to be loaded where.