Allow mode and title to be omitted in options argument for createEditor

[Steve-Mcl]

fixes #3774

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Proposed changes

If options.mode and options.title are missing, ensure the suffix argument of RED.editor.generateViewStateId is something.

This permits creating an editor with minimal options.

NOTE: the user should ALWAYS provide an options object with the target element. In not doing so, the monaco editor has no idea where to display the editor. As a level of compatibility to earlier node-red versions (and to prevent an exception), a hidden element will be auto generated in the event of options or options.element being missing (and a warning will be generated in the browser indicating this) but the UI will not see the editor.

Checklist

• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the forum/slack team.
• I have run grunt to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality

[coveralls]

Coverage increased (+0.03%) to 68.225% when pulling f7120b3 on Steve-Mcl:allow-editor-create-no-title-no-mode into 1b94cc3 on node-red:master.