Implement Compression for Maps

[minus1over12]

Inspired by #38190, I checked how compressible the maps were and got a strong result.

du -ch *.yml
gzip *.yml
du -ch *.gz

Map	Raw	GZipped
Amber	3.3M	320K
Bagel	3.3M	280K
Box	3.7M	312K
CentComm	1.3M	112K
Convex	4.9M	424K
Core	3.0M	264K
Elkridge	2.5M	232K
Fland	4.7M	384K
Gate	4.3M	380K
Loop	2.3M	196K
Marathon	3.0M	248K
Meta	3.8M	316K
Oasis	4.1M	336K
Omega	1.9M	160K
Packed	2.0M	180K
Plasma	3.5M	304K
Reach	360K	36K
Relic	1.1M	84K
Saltern	1.4M	128K
Train	2.4M	176K
Total	56M	4.8M

This would remove any current concerns about maps taking up too much space in the repository by bringing the whole pool down to less than the size of the largest map.

[PJB3005]

Git and downloads already have these compressed. This would at most save 50 MB on disk for dev environments and server deployments. This isn't worth implementing.

Maybe we want to consider this if we ever feel a strong need to switch the map file format off YAML, but we probably aren't doing that any time soon.