EL Merge Client Release Naming

[abcoathup]

@shemnon ice age delay upgrades have been two word glacier names.

Recent execution layer upgrades have used single Devcon city names:

More frequent, smaller hardforks vs. less frequent, larger ones

I suggest to use Devcon locations past Istanbul: (devcon 0: berlin?) devcon 1: london devcon 2: shanghai devcon 3: cancun devcon 4: prague devcon 5: osaka After 2.5 (?) years that would mean we need to have more devcons or switching naming convention