Orion - add search functionality in block selection.

[felix-ht]

First check

• [X] I added a descriptive title to this issue.
• [X] I used the GitHub search to find a similar request and didn't find it.
• [X] I searched the Prefect documentation for this feature.

Prefect Version

2.x

Describe the current behavior

If I define a block as an input for a flow or as a attribute of another block, I get a drop-down in Orion. If the list is long I have to scroll through lots of options.

Describe the proposed behavior

Add search functionality to the drop-down. If I click a field in Orion that is of any block type, I can search through that list by typing.

The behavior would be similar how the search for issues here in GitHub works.

Example Use

This is especially helpful if one has lots of blocks of the same type. Say I have a custom Block called ObjectDetectionModel.

Each of these contains one trained and published model. If I have 100 of these the pure drop-down becomes a pain to use.

Additional context

No response