Save numeric element properties as integers or floats instead of strings

Problem/Motivation

Numeric element properties like #minlength and #maxlength are being saved as strings when they should be cast to integers.

Instead of saving...

textfield:
  '#type': textfield
  '#title': textfield
  '#minlength': '1'
  '#maxlength': '100'
  '#size': '4'

...it should be...

textfield:
  '#type': textfield
  '#title': textfield
  '#minlength': 1
  '#maxlength': 100
  '#size': 4

Proposed resolution

Save numeric element properties as integers or floats instead of strings.

Numeric properties

• autocomplete_limit
• autocomplete_match
• counter_maximum
• counter_minimum
• date_increment
• default_value
• flex
• max
• maxlength
• min
• minlength
• multiple__add_more_items
• multiple__empty_items
• multiple__min_items
• rows
• size
• step

Remaining tasks

• Write code
• Update webform plugin report
• Update existing elements
• Write test
• Write change record

User interface changes

None

API changes

None

Data model changes

Element properties can now use numeric values.

Release notes snippet

TBD