No way for UI to specify skipping a column in aggregations

[mofojed]

Related to Web UI issue: deephaven/web-client-ui#1355

UI is unable to specify columns to ignore in aggregations, as the default operation is Sum, and Skip was removed.

Steps to Reproduce:

1. Open up http://localhost:10000/jsapi/rollup.html, and set a breakpoint in the displayTableDetails function at the top using the developer tools.
2. Refresh the page. When the breakpoint is hit, highlight the table variable and assign it to a global variable, then resume operation
3. In the developer console, execute the following snippet:

// `temp1` should be the name of your global variable the table is assigned to
var totalsTable = await temp1.getTotalsTable({ operationMap: { I: ['Sum', 'Count'] } })
console.log('totals columns: ', totalsTable.columns.map(c => c.name))

Expected Results:
3. Only two columns I__Sum and I__Count should exist in the output, since aggregations were only specified for I

Actual Results:
3. There are three columns, ['I__Sum', 'K', 'I__Count']. K should not be in the totals output as the column was not specified

There is no Skip operation that can be used either, so there does not appear to be a way to not aggregate a specific column.

[niloc132]

There is a bug here, but the sample is wrong too - if not set, TotalsTableConfig.defaultOperation defaults to dh.AggregationOperation.SUM.

Corrected:

 // `temp1` should be the name of your global variable the table is assigned to
var totalsTable = await temp1.getTotalsTable({ operationMap: { I: ['Sum', 'Count'] } , defaultOperation: 'Skip'})
console.log('totals columns: ', totalsTable.columns.map(c => c.name))