Use chosen plugin for script UI values

[will-moore]

Ported from ome/openmicroscopy#6099

See https://forum.image.sc/t/file-browser-in-omero-script-gui/28117/16

To test:

• Use the sample script below to generate a lot of directories to choose from in the script UI (based on use-case and code in the image.sc link above)
• This generates > 2000 items to show in a list in the script UI
• Without this PR, this is one select box and difficult to choose one (see screenshot)
• With this PR you can search by typing (2nd screenshot)
• Run the script - the chosen item appears in the output message

import omero.scripts as scripts
from omero.rtypes import rstring
import os

dir_list = []
for d in os.listdir('/'):
    dir_list.append(d)
    try:
        for f in os.listdir('/' + d):
            dir_list.append("%s/%s" % (d, f))
    except PermissionError:
        print(d, 'PermissionError')
    except NotADirectoryError:
        print(d, 'NotADirectoryError')

dirs = [rstring(d) for d in dir_list]
print(len(dirs))

client = scripts.client(
    'Test_Big_List.py',
    """Test listing lots of dirs""",
    scripts.String("Directories", values = dirs),
)

try:
    script_params = client.getInputs(unwrap=True)
    client.setOutput("Message", rstring(script_params['Directories']))

finally:
    client.closeSession()

[jburel]

Uploaded the script to merge-ci
It is possible to select a folder and filter by typing