feat: fix ignored handlers

[hannahkm]

WIP

Tested w a demo service that wraps net/http handlers and forces them to generate a span. One has an ignore directive. Only the handler without the ignore directive produces a span:

Tested on echo as well:

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.58%. Comparing base (e061d12) to head (9dcb532).
⚠️ Report is 47 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/injector/aspect/join/function.go	77.77%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #756      +/-   ##
==========================================
+ Coverage   65.72%   69.58%   +3.86%     
==========================================
  Files         113      116       +3     
  Lines        7926     6907    -1019     
==========================================
- Hits         5209     4806     -403     
+ Misses       2192     1552     -640     
- Partials      525      549      +24     

Components	Coverage Δ
Generators	83.23% <ø> (+2.98%)	⬆️
Instruments	∅ <ø> (∅)
Go Driver	77.08% <71.15%> (+1.27%)	⬆️
Toolexec Driver	74.73% <100.00%> (+7.20%)	⬆️
Aspects	76.73% <76.50%> (+4.82%)	⬆️
Injector	76.98% <77.10%> (+4.18%)	⬆️
Job Server	67.50% <55.55%> (+1.58%)	⬆️
Other	69.58% <66.61%> (+3.86%)	⬆️

Files with missing lines	Coverage Δ
internal/injector/aspect/join/function.go	72.70% <77.77%> (+6.28%)	⬆️

... and 107 files with indirect coverage changes

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