Bunch of UI improvements

[Amogh-Bharadwaj]

UI Usability Changes

This PR performs a handful of improvements, fixes and changes across the board for our UI.

Create Mirror Page

• Moves Snapshot Number of Tables In Parallel , CDC Staging Path ,Snapshot Staging Path to Advanced Settings
• Publication name is now a dropdown field and is mandatory.
• Table picker now shows the size of every table

Edit Mirror Page

• Added a banner regarding adding tables. This banner pops up only when atleast one table has been selected for addition.
• Made Edit and Back button float to reduce scrolling hassle

Create Peer Pages

• Dropdown now has options for RDS, Azure and GCP
• Errors now show in toast bars
• Added link to corresponding PeerDB doc.