Add ChType_Enum and enable SetChannelEnum.

[kcstonacek]

This pull request is in response to this topic related to populating TuyaMCU enum types in home assistant.

PR includes the following:

• Created two new channel type ChType_Enum ChType_ReadOnlyEnum
• activate and update the dormant code for CMD_SetChannelEnum
• update HTTP interface to support Enum types with <select> html elements.
• set home assistant type to Select for the Enum channels, populated the 'options' defined from SetChannelEnum via discovery
• ReadOnlyEnum channel types are sent to home assistant as Sensors via discovery.
• configured home assistant value and command templates via discovery populated from SetChannelEnum
• contributed to enum self tests

Usage Example:
SetChannelType 1 Enum
SetChannelEnum 1 0:Zero "1:Title One" 4:Four

SetChannelType 1 ReadOnlyEnum
SetChannelEnum 1 1:One "0:Zero" 4:Four

Points to note:

• it appears much of the original Select templates in hass.c that this PR is based on is a work in progress, and as such may require re-work as those progress.
• the javascript blocking refreshes while focus is on a select box is only based on document.activeElement.tagName != "SELECT"
• Added ReadOnlyEnum types to the PR as requested in the topic
• Enum channel types default to TextField when SetChannelEnum has not been defined
• Adding lots of enums to autoexec.bat can lead to low heap issues when performing HA discovery. I observed this in the main build with 15+ channels without Enums, but Enums certainly aren't helping. Some better memory management during discovery is probably needed.

[github-actions]

🎉 This PR is included in version 1.18.194 🎉

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