Remove `Modules/Adapters/OpenThreads`

Summary

Removes the OpenThreads adapters and enables part of the otb::Stopwatch test.

Rationale

This module contains a single Threads::Sleep method that suspends the current thread. The method can be trivially replaced with std functionality.

Implementation Details

Additional notes

Note that this is technically a breaking change.

Modules/ThirdParty/OpenThreads is kept, since it's needed for OSSIM. OTB still links with OpenThreads after this MR.

Copyright

The copyright owner is Laurențiu Nicola and has signed the ORFEO ToolBox Contributor License Agreement.

---

Check before merging:

• All discussions are resolved
• At least 2 votes from core developers, no vote.
• The feature branch is (reasonably) up-to-date with the base branch
• Dashboard is green
• Copyright owner has signed the ORFEO ToolBox Contributor License Agreement