feat: add "withdrawn" and "canceled" speakers and sessions in statistics.

[sachinchauhan2889]

Fixes #fossasia/open-event-frontend#5010

required for fossasia/open-event-frontend#5671

Short description of what this resolves:

On the events dashboard at https://eventyay.com/events/live in the speakers and sessions column the status "Withdrawn" and "Canceled" are missing. This PR add them.

Checklist

• I have read the Contribution & Best practices Guide and my PR follows them.
• My branch is up-to-date with the Upstream development branch.
• The unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

• All the functions created/modified in this PR contain relevant docstrings.

[codecov]

Codecov Report

Merging #7453 (4ebf12c) into development (393bf7a) will decrease coverage by 0.00%.
The diff coverage is 50.00%.

@@               Coverage Diff               @@
##           development    #7453      +/-   ##
===============================================
- Coverage        65.35%   65.34%   -0.01%     
===============================================
  Files              265      265              
  Lines            13231    13239       +8     
===============================================
+ Hits              8647     8651       +4     
- Misses            4584     4588       +4     

Impacted Files	Coverage Δ
app/api/schema/event_statistics.py	65.51% <50.00%> (-2.49%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 393bf7a...4ebf12c. Read the comment docs.