PLATFORM: Add loading state on deleting a variable

[poswalsameer]

Describe the bug
We don't have a loading state on button click while deleting a variable which allows the user to make multiple requests even when one request is ongoing.

Tasks to perform

• Add loading state.
• Handle everything gracefully with toast messages ( toast.dismiss(), toast.loading(), toast.success(), toast.error() )
• Disable the button when the request is going on.

Expected behavior
On clicking once, the user should be able to delete a variable and the request should go single time only.

[chetan102]

/attempt

[github-actions]

Assigned the issue to @chetan102!