DL-2296 - Fix accessibility issues

Fixed following issues:

Duplicate text on check your answers page relating to income tax paid on other taxable income.
'Change' links on CYA page relating to taxable income now cause keyboard focus to be on shifted to the relevant element
New Html component so Yes/No radio buttons and their conditionally revealed text input are grouped in the same form-group and fieldset.
Textarea on 'What are your employment details?' page only has aria-described-by element when error message is shown.
Moved language toggle out of banner in order to eliminate contrast error.

PR for acceptance tests: DL-2296

Checklist

[x] I've made every effort to commit high quality, clean code and I have executed relevant static analyses to be sure
[x] I've included appropriate tests with any code I've added (Unit, Integration, Acceptance etc.)
[x] I've executed the acceptance test pack locally to ensure there are no functional regressions
[x] I've added my code using logical, atomic commits, squashing as appropriate - including the JIRA issue number in the commit message
[x] I've run a dependency check to ensure all dependencies are up to date