Render table in FastBoot

[billdami]

By default, table content is not rendered in FastBoot, as <VerticalCollection>'s occlusion rendering relies on DOM APIs and window measuring to work. We can disable this in FastBoot however, by setting it's @renderAll arg to true when this.fastboot.isFastBoot is true.

A few other changes would also likely need to happen to support this:

• Make sure any DOM-related logic (e.g. updateColumnVisibility()/getElementWidth()) is made fastboot friendly, we should probably just exit out of that logic early in fastboot and make all columns visible (but make sure this has no fallout in layouts/tables with many columns, i.e. make sure the table container crops columns that extend beyond the container width.)
• To assist in the issue mentioned above regarding tables w/many columns and overflowing the available width in the fastboot-rendered version, we could allow columns to optionally define a hideInFastboot: boolean property, so the app could decide what columns are shown/not shown in fastboot.

Alternative Solution

While unlikely, if none of the above is feasible, we could instead not show the table content at all in fastboot, but instead show a loading placeholder/skeleton UI in the fastboot-rendered version. This would most likely be done using https://github.com/michalsnik/ember-content-placeholders which we already use in our apps. The placeholder would mimic a table layout, matching the number of columns w/relative widths, and allow the number of "rows" to be optionally configured via a <Table> arg.

We could also allow passing in a @placeholderComponent={{string}} arg to the <Table> which could be used instead of the default placeholder component for a more custom layout.