Add autocomplete for VM sizes

[timja]

Requires jenkinsci/jenkins#9959

Previously:

On click giant dropdown:

Now:

I want to view D4a's:

D series:

Testing done

Tried various options with filtering to make sure it makes sense. I initially tried combo-box but it didn't give me control over the filtering / searching which was a bit of a pain with the standard/basic prefix and also with just wanting to search e.g D4 and getting sensible results. Autocomplete allowed more power.

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