Add Count column check to cross-product bridge normalization

[kristynchin-olink]

Add Count column check to cross-product bridge normalization

Problem: Provides error with informative text for cross-product bridging when the Count column is missing from either of or both of the datasets.

Solution: Add a check to internal function, norm_internal_cross_product, to ensure that the Count column is present in both dataframes in cross-product normalization.

Key Features:

• Key feature 1: add check that Count column exists in both dataframes used in cross-product bridge normalization
• Key feature 2: add unit test for norm_internal_cross_product to ensure that the error and corresponding text is functioning as expected

Checklist

• Make sure you are requesting to pull a feature/bugfix branch (right side). This should not be main or develop.
• Make sure you are make a pull request against either main or develop (left side). (Requesting to main should be reserved for bugfixes and new releases)
• Add or update unit tests (if applicable)
• Check your code with any unit tests (Run devtools::check() locally)
• Add neccessary documentation (if applicable)

Type of changes

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• Bugfix (non-breaking change which fixes an issue) (link the issue on the right)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code style update (formatting, renaming)
• Documentation Update
• Other (explain)