refactor: rename objects representing workspace

This prevents confusion between the terms "GitLab project" and "VS Code workspace". The current legacy naming that uses the name "project" to represent VS Code workspace is diverging from an established naming and confuses contributors

Examples of where this caused confusion

GitLabService

• fetchCurrentProject returned a GitLab project fetched from the API
• getAllGitlabProjects returned a list of workspaces

StatusBar tests

gitLabService.fetchCurrentPipelineProject.mockReturnValue(project);

These tests were using project which was actually a workspace. The tests were passing because the production logic only checks that the fetchCurrentPipelineProject() method returns something. But the tests were confusing.

MrItemModel

This assignment now makes much more sense:

- workspaceFolder: this.project.uri,
+ workspaceFolder: this.workspace.uri,