[ic-text-field]: character count interferes with validation message on small fields

[GCHQ-Developer-741]

Summary of the bug

When text fields are resized to have a small width, the remaining space for the character count and validation becomes very small and the two elements interfere with one another. 

🪜 How to reproduce

1. Create a Text field with a small defined width
2. Enter above character limit
3. See the error

🧐 Expected behaviour

The validation message and character count should be spaced out nicely

📸 Screenshots or code

Additional info

Explore options to avoid clash between the two elements. 

• Stack elements
• Move character count to title line (top right)
• Positioning dependent on width/breakpoint?

[MI6-255]

The change is to make the validation the same width of the helper text etc

[MI6-255]

Add visual test