Remove unused internal or unexported functions

[alexandear]

This PR removes unused internal or unexported functions reported by the deadcode analyzer.

Details

❯ deadcode ./... | grep internal
internal/action/infocomplete.go:138:6: unreachable func: contains
internal/buffer/line_array.go:289:22: unreachable func: LineArray.deleteByte
internal/config/plugin.go:148:6: unreachable func: FindAnyPlugin
internal/config/rtfiles.go:102:21: unreachable func: namedFile.Name
internal/screen/screen.go:240:6: unreachable func: InitSimScreen
internal/util/profile.go:19:6: unreachable func: Tic
internal/util/profile.go:24:6: unreachable func: Toc
internal/util/util.go:238:6: unreachable func: IsUpperWordChar
internal/util/util.go:244:6: unreachable func: IsLowerWordChar
internal/util/util.go:514:6: unreachable func: ParseSpecial