Override server logging level with environment variable

[ghost]

Description

Use LOG_LEVEL environment variable to override logging level for emu.grasscutter (which also contains all loggers under it). This might help with debugging various issues reported by users. Previously, the only way to override these levels would be to use -Dlogback.configurationFile

Issues fixed by this PR

N/A

Type of changes

• Bug fix
• New feature
• Enhancement
• Documentation

Checklist:

• My code follows the style guidelines of this project
• My pull request is unique and no other pull requests have been opened for these changes
• I have read the Contributing note and Code of conduct
• I am responsible for any copyright issues with my code if it occurs in the future.

[ghost]

Note that I have decided to remove override for emu.grasscutter.scripts.ScriptLib as it can now be toggled globally.

Going forward I ask all contributors to use TRACE for very verbose logging (such as continuous dumping of avatar state) while reserving DEBUG for verbose informational messages (such as singular important actions like starting/stopping internal timers or handling of incorrect, but expected, states).

Here's example for good TRACE logging:

• Current avatar motion state %s, stamina %d/%d

Here's example for good DEBUG logging:

• MOTION_FALL_ON_GROUND received after %dms, discarding