feat: Lower values of char and byte literals

[lnicola]

Closes #12137

[lnicola]

As expected, this doesn't affect the memory usage:

# baseline
Database loaded:     609.77ms, 244minstr, 100mb (metadata 416.03ms, 24minstr, 500kb; build 110.58ms, 8807kinstr, 40kb)
  crates: 39, mods: 878, decls: 20841, fns: 15585
Item Collection:     9.90s, 80ginstr, 375mb
  exprs: 427870, ??ty: 325 (0%), ?ty: 123 (0%), !ty: 1                                                                                                             
Inference:           52.23s, 386ginstr, 729mb
Total:               62.12s, 466ginstr, 1104mb

# pr
Database loaded:     619.90ms, 245minstr, 100mb (metadata 413.23ms, 24minstr, 500kb; build 113.97ms, 8766kinstr, 40kb)
  crates: 39, mods: 878, decls: 20841, fns: 15585
Item Collection:     10.09s, 80ginstr, 375mb
  exprs: 427870, ??ty: 325 (0%), ?ty: 123 (0%), !ty: 1                                                                                                             
Inference:           50.78s, 375ginstr, 729mb
Total:               60.87s, 455ginstr, 1104mb

[lnicola]

[Veykril]

@bors r+

[bors]

📌 Commit 9856144 has been approved by Veykril

[bors]

⌛ Testing commit 9856144 with merge e789d73...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing e789d73 to master...