[Examples] Nullable

[ysolomchenko]

Towards #3958

Changes

Examples mark as nullable

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.26%. Comparing base (6250307) to head (4654711).
Report is 346 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5881      +/-   ##
==========================================
+ Coverage   83.38%   86.26%   +2.87%     
==========================================
  Files         297      257      -40     
  Lines       12531    11219    -1312     
==========================================
- Hits        10449     9678     -771     
+ Misses       2082     1541     -541     

Flag	Coverage Δ
unittests	?
unittests-Project-Experimental	86.25% <ø> (?)
unittests-Project-Stable	86.19% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

see 238 files with indirect coverage changes

[CodeBlanch]

LGTM