define custom regions

[mikev]

Problem Statement:
Often a country or several countries need a custom region, which defines slightly different parameters. For example in Malaysia any frequencies in 924 Mhz are not legal.

Solution:
So we defined a new region AS923_1B which did not use frequency within 924 Mhz. Now Kenya needs this same custom region, because some of our EU868 frequencies are not legal. This will be a recurring pattern. The PR, review, commit process is painful so lets just do this once across all our repos and define EU868_A to _F and AS923_1A .. 1F

Only AS923 and EU868 will require custom regions.

Libraries (Require a review 1st)
helium/proto#250
#1502
helium/erlang-lorawan#27

Projects
helium/miner#1873
https://github.com/helium/gateway-rs/search?q=as923 [gateway-rs no longer requires enum]
helium/sx1302_hal#36
https://github.com/helium/docs/pull/1048/files
helium/helium-config-service#27 (edited)

[madninja]

Note that this unlikely be used in a miner release, unless we need to do another miner release in January, 2023 right?