Scanner bug fixes and button event handling improvements

[penfold42]

Home double tap takes you to page 0

fix splash screen button/encoder handling

Fixed scanning bug when squelch==0 and sped it up

Changed scanner buttons

• Back short click => exit rollback settings (as before)
• Back long press => exit keep current settings (was menu long press)
• Menu short click => Radio options (as before)
• Menu long press => does nothing now

move some code out of button_state computation

• I want to separate out the button_state computation for use elsewhere
• moved any code that doesn't contribute to the computation

ifndef #define M_PI to keep vscode from flagging problems. (the compiler always knew where to find it)

[penfold42]

I've fixed the merge conflict with the U8g2 PR

[dawsonjon]

Cheers