Switch to linux/arm64 images

[VinneyJ]

Description

Switch to building linux/arm64 images (except where we don't have control of the infrastructure e.g. charterAFRICA).

Type of change

• Chore

Screenshots

N/A

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

[kilemensi]

Lets give this the final 👀 @CodeForAfrica/tech before merging. The big difference is switching to linux/arm64 instead of building both linux/amd64 and linux/arm64. This should have minimal impact on build times.

PS: @thepsalmist please follow up to see if we can switch charterAFRICA to arm64 in the future. Otherwise, we'll keep PROD build for charterAFRICA to linux/amd64.