feat(table): enable multiple data rows

[andrewseguin]

Originally at #10964

Introduces a new table input multiTemplateDataRows which allows the table to have multiple data rows per data object.

Old paradigm

Each data object passed to the table is rendered as a data row. Since the mapping is 1:1, the data array itself can be used with the IterableDiffer to determine which rows need to change.

New paradigm

Each data object passed to the table may be rendered by one or more rows. The IterableDiffer cannot use the data array itself anymore since it will not correctly understand add/remove/move operations in the rows.

Instead, the IterableDiffer will be diffed with a DataRow object that represents a pair containing a data object and row template. When the data changes, the list of DataRow objects will be constructed and diffed to get the list of changes.

Caveats for discussion

1. The row context previously contained an index value that represented both the row index and data object index (they were the same. Now, that index value represents the index of the data. To get the row index, there is an additional context property called rowIndex.

Should it be swapped such that index is the row index and the data index can be stored in dataIndex?

2. Similarly, the trackBy function receives an index value. Previously the index matched both the data and row. Now, its explicitly the data index.

Should trackBy receive the row index?

[josephperrott]

LGTM

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