[enhancement] add ability to pass custom timeout for instance boot / initial ssh connection

Currently, it is hardcoded at 40 minutes. For many clouds, if the instance is not up within 1 minute, something is very wrong, and within 5 minutes, you can be 99.99% certain that image is never going to come up.

I want multiple things to be possible:
- Default value is no longer same for all clouds. should be configurable per cloud with conservative default value set in base class.
- Can be passed to cloud constructor or set in pycloudlib.toml per cloud
- Can take into consideration instance type (i.e baremetal will take significantly longer than a VM)
- Can be specified to instance launch() command to override any existing config or default value