lib: add utf16 fast path for TextDecoder

[ChALkeR]

Tracking: #61041

Builds on top of #61549
Like that PR, this is based on the logic in https://github.com/ExodusOSS/bytes

Previously, ICU and string_decoder were used on with-intl and without-intl variants correspondingly for UTF-16 implementation. ICU path was slow, string_decoder path was wrong and lacked BE anyway.

Instead, just use the codepath from #61549 with simple UTF-16 decoding methods.

This:

1. Speeds up utf-16le decoding about 5x
2. Speeds up utf-16be decoding about 3x
3. Adds fatal utf-16le support to without-intl TextDecoder
4. Fixes utf-16le replacement for without-intl TextDecoder, previously it was silently returning wrong results
5. Adds utf-16be support (both fatal and replacement) to without-intl TextDecoder
6. Unifies the logic, using a single codepath everywhere for Unicode

Benchmarks

TODO

[nodejs-github-bot]

Review requested:

• @nodejs/performance
• @nodejs/startup

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.69%. Comparing base (8c57908) to head (2a30acc).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #61559   +/-   ##
=======================================
  Coverage   89.68%   89.69%           
=======================================
  Files         674      674           
  Lines      204048   204057    +9     
  Branches    39166    39174    +8     
=======================================
+ Hits       183003   183020   +17     
+ Misses      13352    13347    -5     
+ Partials     7693     7690    -3     

Files with missing lines	Coverage Δ
lib/internal/encoding.js	99.34% <100.00%> (+2.73%)	⬆️
lib/internal/encoding/util.js	100.00% <100.00%> (ø)

... and 34 files with indirect coverage changes

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