feat: Add upload url validation before making requests

[calvin-codecov]

Closes https://github.com/codecov/core-engineering/issues/52

• Adds validation for various url parts of create_commit, empty_upload, send_create_report, send_reports_result, send_reports_result_get, upload_completion

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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