feat: ensure modules next to tesseract_api.py can always be imported

[dionhaefner]

Relevant issue or PR

#372, esp. discussion here: #372 (comment)

Description of changes

• Tesseract runtime now adds the folder containing tesseract_api.py to PYTHONPATH. This makes it easier to import local modules in all scenarios (containerized vs. non-containerized usage).
• Add a test for both cases.
• Adapt docs for localdependency building block (now called localpackage), which was part mislabeled and part incorrect.

Testing done

CI

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.45%. Comparing base (a2d02b5) to head (bb94f4c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #400      +/-   ##
==========================================
+ Coverage   76.42%   76.45%   +0.03%     
==========================================
  Files          29       29              
  Lines        3359     3364       +5     
  Branches      526      526              
==========================================
+ Hits         2567     2572       +5     
  Misses        558      558              
  Partials      234      234              

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[apaleyes]

terrific! just some tiny comments below