feat: add exections_cancellable to sdk.create and export Execution

[fiedlr]

• add executions_cancellable to GoodDataSdk.create
• Execution() instances are needed for the new cancelation method

risk: high

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.35%. Comparing base (f6d2d7a) to head (4619eb3).
Report is 242 commits behind head on master.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1024      +/-   ##
==========================================
- Coverage   84.37%   83.35%   -1.03%     
==========================================
  Files         141      154      +13     
  Lines        9603    10423     +820     
==========================================
+ Hits         8103     8688     +585     
- Misses       1500     1735     +235     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.