Issue-272: Add String Comparison operators

[Amalicia]

Description

This PR adds the following comparison operators to String columns: <, <=, > and >=.

Whilst I'm touching parts like this if there are any other comparison operators for other types then please let me know, I'm more than happy to add them.

Related Issue and dependencies

• Resolves [Feature request]: Add/review column comparators #272

How Has This Been Tested?

• This pull request contains appropriate tests?:
  • YES
  • New unit tests added for each comparison operator

[github-actions]

This is an auto-generated comment created by:

• Date : 2023-05-12 11:29:22 +0000 (UTC)
• Workflow : PR comment
• Job name : create_test_summary_report
• Run : 4958327544
• Commit : b720a6b Issue-272: Fix formatting

Actor	Triggering actor	Sender
Amalicia	Amalicia	Amalicia
Triggered by: Workflow name: "CI" at .github/workflows/ci.yml URL: https://github.com/hablapps/doric/actions/runs/4958231460 on workflow_run:completed

Test summary report 📊

Spark version	testing
2.4.1
2.4.2
2.4.3
2.4.4
2.4.5
2.4.6
2.4.7
2.4
3.0.0
3.0.1
3.0.2
3.0
3.1.0
3.1.1
3.1.2
3.1
3.2.0
3.2.1
3.2.2
3.2
3.3.0
3.3.1
3.3

[codecov]

Codecov Report

Merging #355 (b720a6b) into main (8eef33d) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #355      +/-   ##
==========================================
+ Coverage   97.60%   97.61%   +0.01%     
==========================================
  Files          62       62              
  Lines        1249     1253       +4     
  Branches       23       16       -7     
==========================================
+ Hits         1219     1223       +4     
  Misses         30       30              

Flag	Coverage Δ
spark-2.4.x	94.68% <100.00%> (+0.02%)	⬆️
spark-3.0.x	96.75% <100.00%> (+0.01%)	⬆️
spark-3.1.x	97.49% <100.00%> (+0.01%)	⬆️
spark-3.2.x	97.71% <100.00%> (+0.01%)	⬆️
spark-3.3.x	97.71% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...re/src/main/scala/doric/syntax/StringColumns.scala	100.00% <100.00%> (ø)

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[alfonsorr]

Thanks!