feat(eslint-plugin): [prefer-output-readonly] support output() function

[reduckted]

Fixes #1871

The prefer-output-readonly rule will now report a problem for any class property that does not have the readonly modifier and has either a type annotation of OutputEmitterRef<T>, or is assigned the result of the output() function.

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• nx run-many -t test --codeCoverage
• nx run-many -t build,typecheck,check-rule-docs,lint,check-rule-lists,check-rule-configs
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.63%. Comparing base (759f07d) to head (8663376).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1876   +/-   ##
=======================================
  Coverage   91.62%   91.63%           
=======================================
  Files         179      179           
  Lines        3380     3383    +3     
  Branches      547      547           
=======================================
+ Hits         3097     3100    +3     
  Misses        144      144           
  Partials      139      139           

Flag	Coverage Δ
unittest	91.63% <100.00%> (+<0.01%)	⬆️

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Files	Coverage Δ
.../eslint-plugin/src/rules/prefer-output-readonly.ts	100.00% <100.00%> (ø)
...plugin/tests/rules/prefer-output-readonly/cases.ts	100.00% <ø> (ø)

[MillerSvt]

Please add support for OutputRef from function outputFromObservable

[reduckted]

Please add support for OutputRef from function outputFromObservable

That should already be handled.

https://github.com/angular-eslint/angular-eslint/pull/1876/files#diff-ad617ad607520c48f95c79841c319e69e8a3beaeda23df74f5715522224a9c86R172

[JamesHenry]

Thank you @reduckted!