Use preferred tile.openstreetmap.org URL

[Firefishy]

TL;DR: use https://tile.openstreetmap.org, no subdomains, no short names.

Many projects, examples, and documentation still use old URLs to access the tile.openstreetmap.org service. The URLs should be updated as follows:

• a.tile.openstreetmap.org -> tile.openstreetmap.org
• b.tile.openstreetmap.org -> tile.openstreetmap.org
• c.tile.openstreetmap.org -> tile.openstreetmap.org
• a.tile.osm.org -> tile.openstreetmap.org
• b.tile.osm.org -> tile.openstreetmap.org
• c.tile.osm.org -> tile.openstreetmap.org
• tile.osm.org -> tile.openstreetmap.org
• http://* -> https:// (use secure URL)

tile.openstreetmap.org supports HTTP/2 and HTTP/3 which no longer require the old (a|b|c) aliases to increase browser connection concurrency. Using a single URL improves performance and ability to cache.

The old URLs have a maintenance burden and add complexity. The old URLs may stop working in the future. Please switch to the preferred URL now.

(This issue is for linking 3rd party projects on Github and elsewhere which are being asked to update tile.openstreetmap.org URLs)