Add support for measure orientation

[lhnguyen-vn]

Thank you for your contribution. You're a :star: already!

Before submitting this PR, please have a look at the below checklist so that we know more about your PR. Please also reference any relevant issues from the issues page if this PR is intended to address one of those.

What does this PR do?

• [x] Describe what your pull request does: TreeParzen only supports minimizing objective function, but not all of MLJ's measures are losses. This PR addresses this by adding a negative sign for score measures.

Checklist

• [x] Your code builds clean without any errors or warnings
• [x] Unit tests have been added for core changes
• [x] julia --project -e 'using Pkg; Pkg.test()' has been run locally and passes
• [x] Documentation has been updated with corresponding changes (if applicable)

cc @ablaom

[ablaom]

cc @kd-iqvia

[kainkad]

Thank you @lhnguyen-vn for your contribution 🌟. The support for measure orientation have now been released and is available in v0.2.6