Freeze BMP readings before deepsleep

[barbudor]

Description:

Related issue (if applicable): fixes #18710

When DeepSleep is used, once BMP has been put to low-power/sleep mode, freezes all measurments until next restarts.
Prevent UI to display wrong value between the start of the deepsleep process and the actual deepsleep (as it seems there is a ~2 sec windows during which the GUI oculd be refreshed with wrong values)

To be tested by @FOTH156 - do not merge before

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.2.0.9
• I accept the CLA.

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