Scaffold-DbContext flag to force update (without deleting other entities)

### What problem are you trying to solve?

I use scaffolding to create EF models for a lot of different databases, some of which I don't own or control in my organization. Because it is database-first, I often need to re-scaffold to update my models to match any table changes, (names/types/sizes).

Example: One table has columns renamed, some columns deleted, some columns added. I can either manually make those changes to match or I can run the `Scaffold-DbContext` command again with a list of all the tables in my model, and use the `-Force` flag. Which forcefully updates all of the tables, even though I know only 1 table had any changes. Which could lead to someone missing a table when using the force, which would then cause other issues. Also when doing a scaffold with 200 tables it can take 20+ minutes to run when I really only need to force update 1 specific table.

### Describe the solution you'd like

I would like to have a flag that implements the `-Force` to update the model, but only need to list that 1 table. The new flag would mean: "do not remove entities that already exist, only force update the tables listed"

Perhaps `-UpdateOnly`

This would be very beneficial for those database-first scenarios, while still allowing use of the scaffolding tool to keep the model in sync with the database, while keeping this fast.