rust-bitcoin / rust-bitcoin / 9044291183

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Merge rust-bitcoin/rust-bitcoin#2759: Bench `base58` encoding and remove `SmallVec` to improve perf

464669052 fix clippy lint by using resize instead of push (Riccardo Casatta)
deeb160b8 remove SmallVec (Riccardo Casatta)
e4b707ba8 add bench for base58::encode_check (Riccardo Casatta)

Pull request description:

  In a downstream app I've seen printing a descriptor is not a cheap operation, analyzing the flamegraph it seems base58 encoding of the xpub is the culprit

  ![image](https://github.com/rust-bitcoin/rust-bitcoin/assets/6470319/30883c6b-7627-4ad0-aa91-373f22393f26)

  This PR adds benches for the `encode_check` function, and add the changes gaining more boost, which is also good cause it removes code.

  Other attempts didn't provide enough benefit for inclusion but I report them here for knowledge.

  ```
  ## baseline

  running 2 tests
  test benches::bench_encode_check_50   ... bench:       8,760 ns/iter (+/- 113)
  test benches::bench_encode_check_xpub ... bench:      19,982 ns/iter (+/- 109)

  ## remove smallvec

  running 2 tests
  test benches::bench_encode_check_50   ... bench:       7,935 ns/iter (+/- 129)
  test benches::bench_encode_check_xpub ... bench:      18,076 ns/iter (+/- 184)

  ## increase smallvec to 128 (fits xpub)

  test benches::bench_encode_check_50   ... bench:       8,786 ns/iter (+/- 738)
  test benches::bench_encode_check_xpub ... bench:      20,006 ns/iter (+/- 2,611)

  ## avoid char-to-str by keeping str map

  test benches::bench_encode_check_50   ... bench:       7,895 ns/iter (+/- 88)
  test benches::bench_encode_check_xpub ... bench:      17,883 ns/iter (+/- 118)
  ```

  Gains are good (~10%), but I don't think they explains the 3ms to print a descriptor in wasm env,
  probably is the sha256 for the checksum is fast in cargo bench but slow in wasm env, but I didn't research on the topic.

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