chore: Improve spanner routing

[codekeyz]

• Remove pharaoh_next framework implementation & tests. No concrete plans to finish and make this usable.
• Improve spanner routing

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.76923% with 15 lines in your changes missing coverage. Please review.

Project coverage is 74.97%. Comparing base (fd75d39) to head (812fd75).

Files with missing lines	Patch %	Lines
packages/pharaoh/lib/src/http/body.dart	64.51%	11 Missing ⚠️
packages/spanner/lib/src/tree/tree.dart	91.66%	2 Missing ⚠️
packages/pharaoh/lib/src/http/response.dart	0.00%	1 Missing ⚠️
packages/pharaoh/lib/src/http/router.dart	0.00%	1 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## main #139 +/- ##
==========================================
+ Coverage 70.87% 74.97% +4.09% 
==========================================
Files 43 30 -13 Lines 1528 1059 -469 ==========================================
- Hits 1083 794 -289 + Misses 445 265 -180 

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