feat: 'group by priority' names are now more readable

[ilandikov]

Description

Change group names from Priority 1: Highest to Highest (and all others too).

Old name	New name
Priority 0: Highest	Highest priority
Priority 1: High	High priority
Priority 2: Medium	Medium priority
Priority 3: None	Normal priority
Priority 4: Low	Low priority
Priority 5: Lowest	Lowest priority

Motivation and Context

Provide shorter group names with only meaningful data.

Fixes #1628

How has this been tested?

Unit tests (Fixed)

Types of changes

Changes visible to users:

• Feature

Checklist

• My code follows the code style of this project and passes yarn run lint.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• My change has adequate Unit Test coverage.

Terms

• My contribution follow this project's contributing guide
• I agree to follow this project's Code of Conduct

[claremacrae]

I'll edit the motives to note that this fixes:

• More readable names in 'group by priority' #1628