Allow number of worker processes to be configurable when starting container

[evanpelle]

right now the number of worker processes is hardcoded, we should be able to pass in the number before we start the Docker container.

[VariableVince]

Reopening since #2776 was reverted: 81ae714 (reason: https://discord.com/channels/1359946986937258015/1359946989046989063/1458593910468378709 and PR #2816 to solve it was closed as non-desireable or non-working probably)