List widget with +200 options refuses to load completely

**Describe the bug**
I have a `list` widget (country picker) with more than 200 entries.
2 issues occur:
1. When editing an already existing record, the value in the `country` field (let's say `united_kingdom`) to which this `list` is writing/reading appears at the top of the list, before the A.
2. After clicking, the options appear, but when scrolling it always gets stuck in the 20th item. When searching though, it works.

Not sure if these 2 are related though.

**To Reproduce**
1. Have a `list` field
2. Give it a list of more than 200 options
3. Save a record with a value that's below the 20th position on the list
4. Go back to edit that record

**Expected behavior**
All options to be available, or at least for it to lazy load them as I scroll.

**Screenshots**

**Applicable Versions:**

- Netlify CMS version: 2.14.6
- Git provider: GitHub
- OS: macOS 11.0.1
- Browser version: Brave v1.16.76
- Node.JS version: 12.17.0

**CMS configuration**
```yml
collections:
- name: 'data'
label: 'Data'
files:
- label: 'Countries'
name: 'country_list'
file: '_data/country_flags.yml'
fields:
- name: 'country_flags'
label: 'Country flags'
widget: 'list'
summary: '{{name}}'
field:
name: 'name'
label: 'Name'
widget: 'string'

- label: 'People'
name: 'people_list'
file: '_data/people.yml'
fields:
- name: 'people'
label: 'People'
widget: 'list'
summary: '{{name}}'
fields:
- name: 'name'
label: 'Name'
widget: 'string'

- name: 'country'
label: 'Country'
widget: 'relation'
collection: 'data'
multiple: false
file: 'country_list'
search_fields: ['country_flags.*']
display_fields: ['country_flags.*']
value_field: 'country_flags.*'

```

`_data/country_flags.yml`:
```yml
country_flags:
- abu_dhabi
- afghanistan
- albania
- algeria
…
- united_kingdom
…
```

`_data/people.yml`:
```yml
people:
- name: 'John Doe'
country: 'united_kingdom'
```