TBI - (fiori-elements-writer): Remove dependency on 'sap.fe.templates' for custom page V4

[martinjanus-sap]

Description (include screenshots)

Feedback from our V4 Fiori elements colleagues about changes to the V4 generated projects (regardless of UI5 version):

• The UI5 dependencies should depend on sap.fe.core for custom page, otherwise in V4 should depend on sap.fe.templates in the manifest.json
• Remove the manifest.json dependency on sap.ushell, it shouldn't be needed.
• The generated flpSandbox.html should pre-load sap.fe.core and sap.fe.templates for better performance where possible.

Value

Align with best practice recommendations from V4 Fiori elements.

Architecture Elaboration

Does it requires architecture elaboration?

Notes

Tasks

• [ ] Task 1