Q3BX: Bazel proof-of-concept

Created by: jhchabran

See https://docs.google.com/document/d/1HYbaYz9GAhjfHKCMgxi8O3Zi6n3uDkezR3pETxjtO8g/edit#heading=h.e0xahoi7r2c7

➡️ This ticket is focusing on building POC to use Bazel.

The potential benefits of moving to Bazel are really high, but so is the cost. We need more clarity around that cost. If we don't do this, we won't be able to understand when such a move is best to be taken, at the cost of investing in solving problems that may be addressed by Bazel further down the line.

@rafax doesn't have the bandwidth to drive the POC, but he can support us, along with @olafurpg. A slack channel has been created for that purpose.