Fetch only required data from Huawei LTE

[scop]

Description:

Don't fetch data that is not going to be used. When debug logging is enabled, still fetch everything in order to provide indication of available/supported data to users, as instructed in docs.

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New or updated dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[pvizeli]

I'm not sure what will be in the right direction. That is more a general question and maybe we should write an architecture about this.

General, I would love to remove the CONF_MONITORED_CONDITIONS. Home Assistant should grab all available data and the user decide on UI what he want to see and in which way.

[scop]

A problem is that it might not be possible to enumerate what "all available data" is, and offering only a subset would not be sustainably maintainable (or would be overly restrictive).

[balloob]

Pascal, I think that the current PR is not related to a discussion about monitored conditions. I would see this as an optimization.