fix(agent): Make build dependencies optional to unbreak install

[Pwuts]

• Fixes cx-freeze fails to install since #7271 #7297

Background

The cx-freeze dependency was changed to a git dependency in #7271. This requires python3-dev to be installed locally to build the cx-freeze package when you run poetry install.

Changes 🏗️

• Create (optional) build dependency group
• Move cx-freeze dependency to build dependency group

To include this group when installing dependencies, run poetry install with the --with=build option.

PR Quality Scorecard ✨

• Have you used the PR description template?   +2 pts
• Is your pull request atomic, focusing on a single change?   +5 pts
• Have you linked the GitHub issue(s) that this PR addresses?   +5 pts
• Have you documented your changes clearly and comprehensively?   +5 pts
• Have you changed or added a feature?   -4 pts
  • Have you added/updated corresponding documentation?   +4 pts
  • Have you added/updated corresponding integration tests?   +5 pts
• Have you changed the behavior of AutoGPT?   -5 pts
  • Have you also run agbenchmark to verify that these changes do not regress performance?   +10 pts

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 35.94%. Comparing base (cbae8b5) to head (39cf2cf).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7298      +/-   ##
==========================================
+ Coverage   27.89%   35.94%   +8.05%     
==========================================
  Files         102       18      -84     
  Lines        6554     1263    -5291     
  Branches      961      191     -770     
==========================================
- Hits         1828      454    -1374     
+ Misses       4642      779    -3863     
+ Partials       84       30      -54     

Flag	Coverage Δ
Linux	35.94% <ø> (+8.05%)	⬆️
Windows	35.80% <ø> (+5.80%)	⬆️
agbenchmark	?
autogpt-agent	35.94% <ø> (ø)
forge	?
macOS	35.94% <ø> (+8.05%)	⬆️

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[Pwuts]

Merging this without waiting on approval because it is an urgent fix