Make websocket timeout configurable

[lbbrhzn]

add the websocket close timout, ping timeout and ping interval to the config flow.
This can be used to finetune the connection with the charger if needed.
In addition it facilitates higher test coverage, by lowering the ping interval.

[codecov]

Codecov Report

Merging #350 (00bf907) into main (3de83f7) will increase coverage by 1.13%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #350      +/-   ##
==========================================
+ Coverage   84.39%   85.53%   +1.13%     
==========================================
  Files          10       10              
  Lines        1160     1168       +8     
  Branches      171      171              
==========================================
+ Hits          979      999      +20     
+ Misses        111       99      -12     
  Partials       70       70              

Impacted Files	Coverage Δ
custom_components/ocpp/config_flow.py	92.00% <ø> (ø)
custom_components/ocpp/api.py	78.21% <100.00%> (+1.79%)	⬆️
custom_components/ocpp/const.py	100.00% <100.00%> (ø)

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