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.

まず、flex compute 提供の UI と、現在 MiB 値を受け付けているメモリーフィールドを見つけ、近くにある UI テストを確認します。既存の設計が単位セレクターをサポートしている場合は、要求された MiB の代替も用意したうえで、ユーザーがデフォルトで 0.5 のような小数値を含む GiB 単位のメモリーを入力できれば完了です。

索引モデルが issue の本文から書いたものです。