fix: improve schema analysis on big collections COMPASS-4154

[mcasimir]

Description

• Remove the document counts before sampling in compass-schema.
• Shows the loading screen in compass-schema in a way that is consistent with what is happening.

Checklist

• New tests and/or benchmarks are included
• Documentation is changed or added

Motivation and Context

• Bugfix
• New feature
• Dependency update
• Misc

Open Questions

Dependents

Types of changes

• Backport Needed
• Patch (non-breaking change which fixes an issue)
• Minor (non-breaking change which adds functionality)
• Major (fix or feature that would cause existing functionality to change)