Increase default VM memory to 2000 MiB and add validation

[MHHukiewitz]

• Increased DEFAULT_VM_MEMORY to 2000
• Raise ValueError if validation of either memory, vcpus or timeout has invalid values.

Suggested value ranges:

• 2000 MiB <= memory <= 8000 MiB
• 1 <= vcpus <= 4
• 1 <= timeout <= 180

[github-actions[bot]]

This PR is categorized as 'BLACK' due to the extensive changes it introduces. The changes include:

• Modification of default values for DEFAULT_VM_MEMORY, DEFAULT_VM_VCPUS, and DEFAULT_VM_TIMEOUT in conf.py.
• Addition of new validation functions (validate_vcpus, validate_memory, validate_timeout) in utils.py.
• Updates to existing functions in authenticated_http.py that include calls to these validation functions.

These changes have a high potential for introducing bugs, as they affect the core functionality of the library by modifying default values and adding new constraints on resource usage. Additionally, the addition of new validation functions requires deep understanding of the project architecture and could introduce new bugs if not implemented correctly.

[hoh]

As discussed in the meeting today, hardcoding such limits in the SDK does not make sense.