UI: Please change memory setting in flex compute offering from MiB to GiB

### The required feature described as a wish

As a user, I'd like to be able to set the memory size of my instances in GiB without having to calculate the correct MiB value.
Entering values in MiB tends to lead to entering round numbers of 1,000. This then results in odd GiB values.
If a VM with less than 1 GiB is ever actually needed, you can enter 0.5 GiB, for example.
However, this use case is likely to occur much less frequently than higher GiB values.

Maybe it could include a drop-down menu next to the value that uses GiB as the default but also allows MiB to be selected. But I think GiB is the most helpful for most people.

Start by locating the flex compute offering UI and the memory field that currently accepts MiB values, then check any nearby UI tests. Done means users can enter memory in GiB by default, including fractional values such as 0.5, with the requested MiB alternative if the existing design supports a unit selector.

Written by the indexing model from the issue text.