[Design] [Form Recognizer | Table Indexer] Implement indexer on ExtractedTable to index into Cells array

Summary

Tables cells are available in Form Recognizer output in order to use them in application UI, rather than for data analysis. Given this, providing a table indexer that allows callers to index into a given cell in the table by row, col, is a more idiomatic approach than having an array of cells users must iterate through to find a given cell.

One question that arises is how to handle column span and row span.

We should understand prior approaches in BCL/.NET and design an approach for indexing into table cells consistent with these.

The resulting API will likely look like:

public class ExtractedTable {
    public ExtractedTableCell[] Cells { get; }
    ...

See: https://github.com/Azure/azure-sdk-for-net/blob/ce046949f17fc4ceeab5c87beb4750047b983565/sdk/formrecognizer/Azure.AI.FormRecognizer/src/ExtractedTable.cs#L24

Goals

• Identify examples of table indexers elsewhere in BCL/.NET to understand precedents
• Design an API for indexing into table cells consistent with other BCL/.NET types
• Review design with feature crew and architects
• Implement design

[pallavit]

Closing this, and will reopen if there is a customer need for this feature.

[maririos]

We will like to get more information about the usage of this feature to help shape the design. Moving to backlog