fix: Improve a couple of error messages for UI components

[FrederikBolding]

Improve a couple of error messages when validating UI components that use the children utility method.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.28%. Comparing base (a8e0d22) to head (0050cdd).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3625   +/-   ##
=======================================
  Coverage   98.28%   98.28%           
=======================================
  Files         417      417           
  Lines       11793    11803   +10     
  Branches     1841     1844    +3     
=======================================
+ Hits        11591    11601   +10     
  Misses        202      202           

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[Mrtenz]

What was this message before? This doesn't seem ideal either 😅

[FrederikBolding]

This is mostly for coverage purposes, not to actually test the error messages. We want to ensure that typedUnion doesn't do something unexpected when *entries is called with a string for example

[FrederikBolding]

E.g.

snaps/packages/snaps-sdk/src/internals/structs.ts

Lines 114 to 120 in a8e0d22

	if (
	!isObject(value) ||
	!hasProperty(value, 'type') ||
	typeof value.type !== 'string'
	) {
	return;
	}