Improve alternative keyboard input method

[ltguillaume]

Is your feature request related to a problem? Please describe. Personally, I think entering a time via a "clock"/"wheel" is very annoying: it's too sensitive and you often end up correcting the value. The alternative (by having to press the keyboard icon every single time) is also deeply flawed:

• It doesn't automatically select the first value
• When pressing the value, it doesn't automatically select the value, so you need to double-press or press backspace (twice) to replace it
• When (automatically) switching from the hour field to the minute field, the value isn't automatically selected either, so you have to remove it manually

Describe the solution you'd like

1. ~An option to always start with the keyboard alternative input method~ Implemented
2. Optional: fill in the suggested time as placeholder values, not as actual values
3. When tapping on the hour/minute field, select all
4. When switching automatically from hour to minute field, select all

Describe alternatives you've considered For reference, Simple Alarm Clock (https://github.com/yuriykulikov/AlarmClock) has this feature and it's great.