[Projects] Adding allow_cross_project flag for creating project from template

[roei3000b]

Breaking change in this PR
We change the way the following functions behave:

1. get_or_create_project
2. load_project

From now, if the loaded project name(from yaml file) != provided name we will raise Exception and the regular flow of the code will break.

For example, following snippet that worked until this change:

import mlrun
project = mlrun.get_or_create_project(
            "run-with-source-and-auto-build"
        )

# do stuff with project

After this change, if the project name from the context != "run-with-source-and-auto-build" it will break this code.
There are 3 ways for fixing it:

1. Set the allow_cross_project=True when loading the project.
2. Delete the existing project yaml, or ensure its name is equal to the provided name(run-with-source-and-auto-build)
3. Use different project context dir.

https://iguazio.atlassian.net/browse/ML-6300

[liranbg]

some wordings and consistency