Zigbee added recording of when the battery was last reported

[s-hadinger]

Description:

Zigbee is now recording the time when the battery status was last sent.

ZbInfo has a new field BatteryLastSeenEpoch field with the timestamp when the battery was last reported, or none if the timestamp is unknown.

The Web UI now has the duration since last battery status reported as a tool tip, and the color grays out if the time is over 2 days or over 7 days.

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.4.9
• The code change is tested and works with Tasmota core ESP32 V.2.0.4.1
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass