Fix bayonets breaking gun mode selection and pistol bayonet not working

[Coolthulhu]

Summary

SUMMARY: Bugfixes "Fix bayonets breaking gun mode selection and pistol bayonet not working"

Purpose of change

Describe the solution

Rewrote the gun mode selection to avoid the ugly offset math thing.

Added a flag for bayonets so that they don't need a reach attack mode to work.

Describe alternatives you've considered

Testing

• Spawn gun+bayonet+rail xbow and attach mods to gun
• Change firing modes from aim menu to see if all can be picked
• Test modes to see if they work
• Spawn a pistol bayonet and attach it to a pistol
• Look at the statblock to see that it has pierce damage listed

Additional context