feat(adk): add execute backend&tool

[meguminnnnnnnnn]

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[codecov]

Codecov Report

❌ Patch coverage is 64.10256% with 70 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.78%. Comparing base (9e6963f) to head (1d5dc79).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
adk/middlewares/filesystem/filesystem.go	50.00%	36 Missing and 5 partials ⚠️
adk/middlewares/reduction/tool_result.go	0.00%	18 Missing ⚠️
adk/middlewares/reduction/large_tool_result.go	90.80%	4 Missing and 4 partials ⚠️
adk/middlewares/reduction/clear_tool_result.go	50.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #682      +/-   ##
==========================================
+ Coverage   81.59%   81.78%   +0.18%     
==========================================
  Files         127      129       +2     
  Lines       12253    12419     +166     
==========================================
+ Hits         9998    10157     +159     
+ Misses       1512     1506       -6     
- Partials      743      756      +13     

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