tr: refactor and introduce simd to get important perf win

[sylvestre]

after #8439

With:
dd if=/dev/zero bs=1M count=100 | tr '\0' 'x' > 100mb_input

hyperfine --export-markdown tr.md --warmup 3 \
    '/usr/bin/tr a b < 100mb_input > /dev/null' \
    './target/release/tr a b < 100mb_input > /dev/null'     './target/release/tr.previous a b < 100mb_input > /dev/null'
Benchmark 1: /usr/bin/tr a b < 100mb_input > /dev/null
  Time (mean ± σ):      46.4 ms ±   5.4 ms    [User: 32.4 ms, System: 14.0 ms]
  Range (min … max):    40.2 ms …  63.9 ms    66 runs
 
Benchmark 2: ./target/release/tr a b < 100mb_input > /dev/null
  Time (mean ± σ):      29.3 ms ±   6.6 ms    [User: 14.0 ms, System: 15.2 ms]
  Range (min … max):    21.1 ms …  59.1 ms    91 runs
 
Benchmark 3: ./target/release/tr.previous a b < 100mb_input > /dev/null
  Time (mean ± σ):      85.0 ms ±   3.7 ms    [User: 71.9 ms, System: 13.0 ms]
  Range (min … max):    80.6 ms …  93.3 ms    34 runs
 
Summary
  ./target/release/tr a b < 100mb_input > /dev/null ran
    1.58 ± 0.40 times faster than /usr/bin/tr a b < 100mb_input > /dev/null
    2.90 ± 0.67 times faster than ./target/release/tr.previous a b < 100mb_input > /dev/null

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
/usr/bin/tr a b < 100mb_input > /dev/null	46.4 ± 5.4	40.2	63.9	1.58 ± 0.40
./target/release/tr a b < 100mb_input > /dev/null	29.3 ± 6.6	21.1	59.1	1.00
./target/release/tr.previous a b < 100mb_input > /dev/null	85.0 ± 3.7	80.6	93.3	2.90 ± 0.67

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[cakebaker]

Is transform necessary? This function is called only by TranslateOperation and thus it might make sense to adapt the function for this single use case, similar to process_single_delete and DeleteOperation.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/misc/stdbuf (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)