Fix depiction of defaults and organise them

[Amogh-Bharadwaj]

Fixes issues where some params in overview page would show '0' but they would actually have a default value

Organise default values of : Snapshot number of tables in parallel Snapshot number of workers Snapshot number of rows per partition Pull batch Size Sync interval

to constant files in Go and UI

Show these defaults when not set in UI (happens when mirror is created via query layer) Also show publication name in UI

Functionally tested with creating a mirror from UI and Query Layer

[serprex]

not sure if addressed here, but important to differentiate between explicit value matching default & default. For if default changes. Rendering default as placeholder could work

[heavycrystal]

will be fixed upstream