Allow for custom labels for sessions instead of numbers

[alexwykoff]

• Did you search for similar issues before submitting this one?
  Yes

• Describe the issue you encountered:
  When using sessions, just using numbers is not as obvious as a name or label.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  All

• Brave Version (revision SHA):

0.21.0

[alexwykoff]

@bradleyrichter is going to hunt for the dupe 📦

[bsclifton]

related:
the interface for session tabs is awkward #7783
Session tabs grouped by color. #5643
Create about:sessions for session-management #5388
Context menu to open in session tab: X for all available sessions #788

[eljuno]

+1 from community about ability to set a custom name for session tab https://community.brave.com/t/session-tabs-names-and-color/11974?u=eljuno

[bsclifton]

Closing in favor of brave/brave-browser#34