Add Object Store Toolkit as project dependency
This MR adds our Object Store Toolkit (ostk) as a project dependency, pulling it in through cmake fetch content.
The changes are:
- Only run cmake configure rather than full build during Lint ci stage - this saves some build time.
- Add ostk fetch in top level cmakelists and use its cmake modules to get catch2 and json dependency.
- Add openssl, curl and libxml as apt dependencies in the ci.