[EuiSwitch] The contrast ratio of unchecked switches is below the WCAG threshold

[morhof]

WCAG success criterion 1.4.11 - non-text contrast - AA

Steps to reproduce

1. Click on Dashboard
2. Select Create

Actual Result

• The following contrast ratios of interactive elements do not conform to the minimum contrast requirements of 3:1. Therefore, these elements are more difficult to perceive, and may be completely missed by users with low vision:
  Borders of checkboxes 1,6:1,
  Toggle-switches 1,2:1.

Expected Result

• Between foreground and background, the minimum contrast ratio should be 3:1
• For disabled switch the label should be marked as disabled too
• If the switch is in status "off", the contrast requirement must be met

Meta Issue
n.a.

Kibana Version:
8.3
OS:
Microsoft Windows 10 Enterprise (64-bit)
Browser:
Google Chrome 109.0.5414.75 (64-Bit)

Screen reader:
n.a.

Relevant WCAG Criteria:
WCAG success criterion 1.4.11 - non-text contrast - AA
https://www.w3.org/WAI/WCAG21/Understanding/non-text-contrast.html

Relevant ARIA spec:
n.a.

[elasticmachine]

Pinging @elastic/kibana-accessibility (Project:Accessibility)

[cee-chen]

Transferring this to the EUI repo.