Use power saving mode on MAX17043 when entering deepsleep

[blacknell]

Description:

The MAX17043 has a power save mode that can be enabled via a configuration command. This PR takes advantage of this when entering deep sleep and then disables it on restart. It's worth noting that when in power save mode the voltage on the battery isn't actively measured of course but the battery modeling scheme picks up where it left off on restart. This retains the advantages discussed in #19412 which assumes power is maintained to the MAX17043 during deep sleep and the long term battery behaviour can be 'learnt'.

I've seen a dramatic reduction is current draw in tests - a DFRobot ESP32 Firebeetle with DFRobot MAX17043 battery gauge breakout board current draw decreased from 430µA to 10µA.

I've tested on ESP32 but don't have the hardware to test on 8266 (although it builds).

add: use power saving mode when entering deepsleep

Related issue (if applicable): fixes # n/a

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.2.0.14
• I accept the CLA.

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

[arendst]

Oops. Your previous PR is already merged. Pls rebase.