Fix for #4274 string comparison issue in ChartData::getDataSetByLabel

[PeterKaminski09]

Fixes an issue with string comparison in ChartData for finding a dataset by its label (Fixes #4274)

ChartData::getDataSetByLabel has a bug where the string comparison is checking the same string against itself due to the functions parameter having the same name as a variable within the closures scope. This change renames the variable to fix the issue.

Issue Link 🔗

#4274

Goals ⚽

• Fixes the bug
• Adds some unit tests to prevent the relevant issue from regressing

Implementation Details 🚧

• No major changes here, just a quick fix

Testing Details 🔍

• Added some tests that check case sensitivity
• Added some tests that ignore case
• Added some tests that check for the expected nil case

[codecov-io]

Codecov Report

Merging #4275 into master will increase coverage by 0.31%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4275      +/-   ##
==========================================
+ Coverage    41.5%   41.82%   +0.31%     
==========================================
  Files         123      124       +1     
  Lines       14069    14103      +34     
==========================================
+ Hits         5840     5899      +59     
+ Misses       8229     8204      -25

Impacted Files	Coverage Δ
ChartDataTests.swift	100% <100%> (ø)
...arts/Data/Implementations/Standard/ChartData.swift	58.84% <100%> (+7.08%)	⬆️
...ta/Implementations/Standard/ScatterChartData.swift	25% <0%> (+25%)	⬆️

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[danielgindi]

What a funny bug. Thank you!