[SSF-105] Combine Standard and Lead Volunteers

[dburkhart07]

ℹ️ Issue

Closes #105

📝 Description

• Adjusted the Role enum to combine both STANDARD_VOLUNTEER and LEAD_VOLUNTEER to just a VOLUNTEER role
• Removed volunteer type filtering in the volunteer management
• Performed migration to rewrite the database enum and its usage within the user table
• Removed mentions of either role everywhere in the code

✔️ Verification

Verified all the endpoints still work:

Made sure volunteer management had the volunteer type removed:

[sam-schu]

It looks like it might be possible to update an enum type column by creating a new enum type, switching the column to use the new type, and then deleting the old enum, rather than dropping and re-adding the entire column (which would mess up dummy data). Can you look into this?

[Juwang110]

Everything lgtm!

[sam-schu]

Looking good!

[sam-schu]

Could we format this more readably or is Prettier making it look like this? (same for the down migration)