Rename standard_filter.vue to simple_filter.vue

What does this MR do?

On the vulnerability report, there is a list of filter dropdowns:

This MR renames standard_filter.vue to simple_filter.vue, which is used for a number of the filters:

Originally, most of the filters were standard dropdowns, with one or two custom dropdowns. However, nowadays half of the filters are custom dropdowns, and we see the need to convert more of them over. As a result, there will eventually be more custom dropdowns that standard ones, and the name standard doesn't really fit anymore.

Renaming it to simple better describes what it is: a simple dropdown that shows a flat list with simple behavior:

Simple dropdown with simple behavior	Custom dropdown with more complex behavior

Does this MR meet the acceptance criteria?

Conformity

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• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

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