Add an attribute encoding helper.

[ChadSikorra]

This is a tradeoff to keep ASN1 logic in this library, but provide a fast-path helper for LDAP. The performance gains of doing this are enough to warrant it. Attribute encoding on searches is very CPU intensive and this helps for large searches / lots of entries / lots of attributes. This will be used in the LDAP library as a way to optimize server side entry attribute encoding. I've already benchmarked the changes on the LDAP side and it's a roughly 40% encoding savings on searches.

[codecov]

Codecov Report

❌ Patch coverage is 98.18182% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.55%. Comparing base (b57a38f) to head (9e0f2d0).

Files with missing lines	Patch %	Lines
src/FreeDSx/Asn1/Encoder/LengthEncodingTrait.php	88.88%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #15      +/-   ##
============================================
+ Coverage     95.13%   95.55%   +0.41%     
- Complexity      382      399      +17     
============================================
  Files            24       27       +3     
  Lines           967     1013      +46     
============================================
+ Hits            920      968      +48     
+ Misses           47       45       -2     

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