File upload support from resource config UI

[nmbr7]

• Add support for file upload field in resource config UI.
• Will need updates in the codegen project to emit file type field for UITemplate data type.
• File upload API support in the backend server
  • File will be uploaded on saving the config
  • FIle content will be saved in the data folder and reference Id will be saved in the DB
  • File will be copied to Pulumi stack-related folder while deploying