option to setup ProcessStartupTimeout

### Description

I got an issue recently with function app start due to ProcessStartupTimeout is 60 seconds.
we got lot of dependencies and key vaults with lot of secrets which make our function startup to go beyond 60 seconds. It would be better if we can get startup time configurable at least when function app run in container environment.

Start by locating where ProcessStartupTimeout is defined and enforced in the Azure Functions .NET worker, then review how container-based function apps receive configuration. Done means the startup timeout can be configured for container deployments and the requested startup scenario no longer fails at the fixed 60-second limit.

Written by the indexing model from the issue text.