fix(bw): 'keys' debug view update

[philmoz]

The 'Keys' debug view on 128x64 B&W radios has some issues with newer radios that have more than 4 trim switches.

Changes:

• move 'Trim - +' string into the header to make room for more trims
• show up to 7 trims
• invert stick icons to be less intrusive
• display Tx instead of invalid trim icon for T5 - T7
• fix 'sticks' icon symmetry

Note: T8 is not displayed for radios with 8 trims.

Before:

After:

[pfeerick]

I wonder if we can just do away with the TRIM -+ to get the eighth trim row... it's not like any of the other switches have headings... plus since it's a debug/diagnostics page I think some RTM to understand anything that isn't immediately clear is acceptable. The alternative being a seperate page for the trims, but I'm not sure that is warranted here.

[philmoz]

Updated to hide the trim header in order to show 8th trim. If less than 8 trims the header is still shown.