[MD] Optimize text content and layout with UX inputs

[noCharger]

• 1. the content for delete button confirmation box

Use case 1 - This is the screenshot of delete button confirmation box in editing credential page:

Use case 2 - This is the screenshot of listing page delete button from Saved Object section, just want to confirm the design for credential listing page delete button confirmation box.

• 2. list page columns to expose, and respective column names [Done]
  
• 3. toast message for success and error

Questions:

1. Do we need a toast for create/edit succesfully? What's the text content for the toast?
2. Do we need a toast for create/edit failed? What's the context for the toast? Shall we expose item ID?

Context - Index pattern management page

Context - Inside Saved object management page

• 4. Context of header
  See screen shots
  [MD] Add header for editing page #2051

• 5. Edit credential page

[kristenTian]

What is the error case for 3, and 4? Could you specify how you produced them