fix: LEAP-245: make Number tag complain about missing to_name

[Gondragos]

<Number/> tag didn't throw validation error if there is missing property of toName.

PR fulfills these requirements

• Tests for the changes have been added/updated
• Docs have been added/updated
• Best efforts were made to ensure docs/code are concise and coherent (checked for spelling/grammatical errors, commented out code, debug logs etc.)
• Self-reviewed and ran all changes on a local instance

This change affects (describe how if yes)

• Performance
• Security
• UX

Does this PR introduce a breaking change?

• Yes, and covered entirely by feature flag(s)
• Yes, and covered partially by feature flag(s)
• No
• Not sure (briefly explain the situation below)

What level of testing was included in the change?

• e2e (codecept)
• integration (cypress)
• unit (jest)
• python!

Which logical domain(s) does this change affect?

Config Validation, Number, Labeling Interface, Creating Project

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5d6ddac) 75.88% compared to head (02f1dd5) 75.89%.
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #5408   +/-   ##
========================================
  Coverage    75.88%   75.89%           
========================================
  Files          154      154           
  Lines        12931    12931           
========================================
+ Hits          9813     9814    +1     
+ Misses        3118     3117    -1     

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[jombooth]

LGTM, please fill in the description!