WIP: Kconfig

[nwf]

WIP on #3130

• Define Kconfig files for user_modules.h
• Define Kconfig files for most of user_config.h
• Deal with the rest of user_config.h
• Wire up .config generation
• Replace use of CPP symbols with Kconfig symbols
• user_mbedtls.h ?
• user_modules.h -> .config script?
• cloud builder

I will eagerly accept help on any of this. :)

• This PR is for the dev branch rather than for master.
• This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• I have thoroughly tested my contribution.
• The code changes are reflected in the documentation at docs/*.

[jmattsson]

Can I please suggest that this goes into the components/platform/Kconfig to match the esp32 branch? And we probably include the word "NodeMCU" in the menu name to make it easier to spot among the IDF things (especially on the esp32 IDF these days).

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.