Block Library: Column: Move resizing controls to Columns block

[aduth]

Previously: #15499
Related (potentially blocked by): #7694

As of #15499, it is possible to resize a Column block using the "Percentage width" input in the block inspector. The usability of selecting an individual Column block is quite poor, however. Per @jasmussen's comment at #15499 (comment) and prior consideration at #7694, we should consider moving the column resizing controls to the parent Columns block, and prevent individual columns from being selected at all.

[paaljoachim]

Can we close this issue?

@jasmussen

[jasmussen]

We can close and reopen if someone wants to work on it. I see the solution as there being resize handles directly on the columns block.

[paaljoachim]

Closing for now.