chore(performance): Use simd for base64 encoding/decoding

[JakubOnderka]

Summary

Use SIMD instructions when doing base64 encoding/decoding. base64 encoding/decoding is common when processing logs, so it would be nice to use SIMD powered algo. base64-simd crate is already used by vector.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Standard tests.

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on
  our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Our CONTRIBUTING.md is a good starting place.
• If this PR introduces changes to LICENSE-3rdparty.csv, please
  run dd-rust-license-tool write and commit the changes. More details here.
• For new VRL functions, please also create a sibling PR in Vector to document the new function.

[pront]

Hi @JakubOnderka, did you get compare numbers for this?

[JakubOnderka]

% cargo bench --all-features base64
vrl_stdlib/functions/decode_base64/literal
                        time:   [55.005 ns 55.128 ns 55.258 ns]
                        thrpt:  [18.097 Melem/s 18.140 Melem/s 18.180 Melem/s]
                 change:
                        time:   [-30.458% -30.269% -30.095%] (p = 0.00 < 0.05)
                        thrpt:  [+43.051% +43.407% +43.798%]
                        Performance has improved.
Found 5 outliers among 100 measurements (5.00%)
  4 (4.00%) high mild
  1 (1.00%) high severe

vrl_stdlib/functions/encode_base64/literal
                        time:   [48.520 ns 48.602 ns 48.696 ns]
                        thrpt:  [20.535 Melem/s 20.575 Melem/s 20.610 Melem/s]
                 change:
                        time:   [-32.638% -32.400% -32.112%] (p = 0.00 < 0.05)
                        thrpt:  [+47.302% +47.930% +48.451%]
                        Performance has improved.
Found 17 outliers among 100 measurements (17.00%)
  9 (9.00%) high mild
  8 (8.00%) high severe

Measured on Apple M2. Results can differ for x86_64 as it supports different SIMD instructions set. Also the benchmark encode/decode very short text, for longer strings it will be even faster.