Make UI tab completer list use Vec<&str> instead of Vec<String>

[fsktom]

Don't know how feasible this is or if it's necessary.

See 275b337

[fsktom]

Actually internally, rustyline prefers &str
https://docs.rs/rustyline/latest/rustyline/completion/trait.Completer.html
https://docs.rs/rustyline/latest/rustyline/completion/trait.Candidate.html

but I'd have to figure it out with the lifetimes somehow
seems quite painful

[fsktom]

The problem is that SongEntries.artists() is pretty slow
in cargo bench it takes 2.5ms while albums(&asp) takes below a ms
I figured it may be due to allocations of Strings but idk

[fsktom]

Well.... turns out I basically did this automatically with #62 xd
And the problem of dealing with lifetimes solved itself by using Rc :D

[fsktom]

Performance improvements in 21bf2b3
From

artists_vec             time:   [2.7070 ms 2.7476 ms 2.7971 ms]
Found 10 outliers among 100 measurements (10.00%)
  6 (6.00%) high mild
  4 (4.00%) high severe

albums_vec              time:   [255.43 µs 261.76 µs 269.15 µs]
Found 5 outliers among 100 measurements (5.00%)
  1 (1.00%) high mild
  4 (4.00%) high severe

to

artists_vec             time:   [1.5549 ms 1.5785 ms 1.6062 ms]
                        change: [-44.196% -43.033% -41.859%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 6 outliers among 100 measurements (6.00%)
  3 (3.00%) high mild
  3 (3.00%) high severe

albums_vec              time:   [202.15 µs 203.30 µs 204.42 µs]
                        change: [-22.566% -21.586% -20.714%] (p = 0.00 < 0.05)
                        Performance has improved.