Clean up Attribution Internals TypeScript

This CL contains no functional changes, but does:

- Use readonly annotations where applicable
- Use visibility annotations where applicable
- Use parameter properties in constructors where applicable
- Make Column::compare optional instead of nullable
- Require TableModel properties to be specified in its constructor
- Make TableModel::getRows abstract
- Remove unused compare parameter from ValueColumn constructor
- Share common columns between EventLevelReportTableModel and
  AggregatableAttributionReportTableModel
- Remove explicit casts from ReportTableModel subclasses by making
  ReportTableModel generic across the actual Report subclass

Change-Id: I0b4f287fd65fc29cadbfaff6f3a9e9d30c77e3a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4106909
Reviewed-by: Nan Lin <linnan@chromium.org>
Quick-Run: Andrew Paseltiner <apaseltiner@chromium.org>
Commit-Queue: Andrew Paseltiner <apaseltiner@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1083156}