More map selector related changes

[tsa96]

• Adds simple header to the static map lists (4 byte: ident, 4 byte: length of uncompressed length, 4 byte: total number of maps). Makes decompressing in game code a lot nicer.

Checks

• !! DONT IGNORE ME !! I have ran nx run db:create-migration <name> and committed the migration if I've made DB schema changes
• I have included/updated tests where applicable (see Testing)
• I have followed semantic commit messages e.g. feat: Add foo, chore: Update bar, etc...
• My branch has a clear history of changes that can be easy to follow when being reviewed commit-by-commit
• My branch is functionally complete; the only changes to be done will be those potentially requested in code review
• All changes requested in review have been fixuped into my original commits

[tsa96]

Oops, #1064 superseded this.