Validate disabled function logic for worker indexing

[surgupta-msft]

1. If worker says that a function is disabled, should the host filter that function out and not send its LoadRequest (and hence, InvocationRequest)? If yes, then need to validate if code is showing this behaviour and correct if needed.

2. Need to validate if host is properly populating disabled func indicators returned by the worker. From this code, it does not seem that we are reading "Properties" which contains disabled key. Need to validate and correct if needed.

[surgupta-msft]

1. Host sends LoadRequest for disabled function as it is invocable using the portal and admin endpoints. We also load disabled functions after enabled functions to avoid unnecessary performance issues. Refer PR Load disabled functions last #5072. Adding comment in code to explain this flow and avoid confusion in future - Added comment to explain disabled function flow #8099

2. Disabling Functions is supported only via AppSettings and not through payload/Function.json.