chore(traits): add Display and FromStr traits

[joshka]

Use strum for most of these, with a couple of manual implementations, and
related tests

Fixes #307

note: this is mainly the enums, the structs tend not to have obvious display representations.

ping @TieWay59 (due to previous work on trait impls)

[codecov]

Codecov Report

Merging #425 (3c455bf) into main (6153371) will increase coverage by 0.69%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #425      +/-   ##
==========================================
+ Coverage   86.41%   87.11%   +0.69%     
==========================================
  Files          40       40              
  Lines        9432     9818     +386     
==========================================
+ Hits         8151     8553     +402     
+ Misses       1281     1265      -16     

Files Changed	Coverage Δ
src/backend/mod.rs	82.92% <100.00%> (+49.59%)	⬆️
src/layout.rs	98.48% <100.00%> (+1.76%)	⬆️
src/symbols.rs	72.41% <100.00%> (+29.55%)	⬆️
src/terminal.rs	58.30% <100.00%> (+2.56%)	⬆️
src/title.rs	100.00% <100.00%> (ø)
src/widgets/block.rs	86.47% <100.00%> (+0.28%)	⬆️
src/widgets/canvas/map.rs	55.55% <100.00%> (+55.55%)	⬆️
src/widgets/chart.rs	97.84% <100.00%> (+0.05%)	⬆️
src/widgets/scrollbar.rs	90.22% <100.00%> (+1.19%)	⬆️
src/widgets/sparkline.rs	91.12% <100.00%> (+1.86%)	⬆️
... and 1 more