Improved JVM Flagging

[ajsea1sy]

Please confirm the following.

• I checked the existing issues for duplicate feature requests

What parts of Modrinth is your feature request related too?

Modrinth App

Is your suggested feature related to a problem? Please describe.

More than 1 report. However, they are closely related

1. Unable to set the initial memory easily alongside the Allocated Memory slider. (Feature request)
2. Some JVM flags will leave Modrinth App hanging (stuck on "Starting...) if typed wrong. (Bug report)

Describe the solution you'd like

1. Intitial allocated memory slider alongside the pre-existing Custom Memory Allocated slider.
2. Fallbacks or errors when Modrinth can't process a JVM flag, prevents getting stuck.

Describe alternatives you've considered

No response

Additional context