New expression functions: compare, string functions and more

[olemartinorg]

Description

This implements the following new expression functions:

• countDataElements - counts the number of data elements in the current instance, given a type. Can for example count attachments or subform elements.
• compare
  • Including the operators equals, greaterThan, greaterThanEq, lessThan and lessThanEq - all of which had dedicated functions already
  • isBefore, isBeforeEq, isAfter, isAfterEq and isSameDay - these are all brand new, and relies on date parsing
• stringIndexOf, stringReplace, stringSlice, lowerCaseFirst and upperCaseFirst

Also, review comments from #2948 have also been solved here.

Related Issue(s)

• Multiple new expression functions app-lib-dotnet#1067
• More expression functions #1299
• Dato i dynamikk med Expression #2122

Verification/QA

• Manual functionality testing
  • I have tested these changes manually
  • Creator of the original issue (or service owner) has been contacted for manual testing (or will be contacted when released in alpha)
  • No testing done/necessary
• Automated tests
  • Unit test(s) have been added/updated
  • Cypress E2E test(s) have been added/updated
  • No automatic tests are needed here (no functional changes/additions)
  • I want someone to help me make some tests
• UU/WCAG (follow these guidelines until we have our own)
  • I have tested with a screen reader/keyboard navigation/automated wcag validator
  • No testing done/necessary (no DOM/visual changes)
  • I want someone to help me perform accessibility testing
• User documentation @ altinn-studio-docs
  • Has been added/updated
    • New expression functions altinn-studio-docs#1983
  • No functionality has been changed/added, so no documentation is needed
  • I will do that later/have created an issue
• Support in Altinn Studio
  • Issue(s) created for support in Studio
  • This change/feature does not require any changes to Altinn Studio
• Sprint board
  • The original issue (or this PR itself) has been added to the Team Apps project and to the current sprint board
  • I don't have permissions to do that, please help me out
• Labels
  • I have added a kind/* label to this PR for proper release notes grouping
  • I don't have permissions to add labels, please help me out

[sonarqubecloud]

Quality Gate passed

Issues
15 New issues
0 Accepted issues

Measures
0 Security Hotspots
89.8% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud