Solve UI bugs of validation loading spinner

[RidhamShah]

Solved

For Import Experiment

• Swagger for validation and import now called through POST
• Swagger is updated to contain details of API
• In UI, the import button for experiments will be disabled until validations are completed
• Spinner will be shown while validations are processing for import
• FIXED - Spamming the import button leads to multiple import calls resulting in multiple imports of the same files.

For import Segment

• In UI, the import button for experiments will be disabled until validations are completed
• Created spinner while validations are processing for import
• FIXED - Spamming the import button leads to multiple import calls resulting in multiple imports of the same files.

[VivekFitkariwala]

I have added one improvement in the comment.