Updating serverless documentation as part of rewrite

[DavidatVast]

Self explanatory - rewrote / re-ordered serverless documentation

https://vastai.atlassian.net/browse/AUTO-1104

[robertfernandez-vast]

Developers want to use serverless. Based off of this fact, the following should be assumed true:

1. For a developer to use serverless, they must know how to set-up their serverless environment.
2. For a developer to use serverless, they must know how to interact with their serverless environment.
3. For a developer to use serverless, they must know how to maintain their serverless environment.

All sections should serve and be organized based off of these statements.

Users can set-up their serverless environment via:

• The vast website
• The vast-sdk
• The vast cli

We should have sections which serve each of these form factors.

Setting up their serverless environment includes:

• Creating and destroying endpoints and what that does to their data and serverless environment
• Creating and destroying workergroups and what that does to their data and serverless environment
• Using our predefined templates or defining custom templates
  • This includes instructing developers on how to make their own pyworkers for their own use cases.
• Addressing frequently occurring questions/pain points with set-up
  • Why does it take so long for workers to load?
  • How do I know when my serverless environment is ready for use?
  • How do I know what serverless environment is best suited for my use case?
• Definitions for each worker state and how to understand how to use these states to get your serverless environment setup.

Users can interact with their serverless environment via:

• The vast-sdk
• The vast-cli

We should organize the sections so that it is clear to developers how they interact with serverless for each form factor.

Interacting includes:

• How to send requests to your endpoint group once its set-up

Users can maintain their serverless environment via:

• The vast website
• The vast-sdk
• The vast-cli

We should organize the sections so that it is clear how they maintain their serverless environment.

Maintaining includes:

• Paying for their serverless environment
• Keeping their pyworkers up-to-date
• Best Practices for keeping their data safe (ex: backing up data)
• Describing what our metrics mean on the endpoint page, and what assumptions go into each metric. (Units, limitations, definitions)
• How to understand how your serverless environment is behaving based on worker states.