Add support for more customizable input

[david0xd]

This PR adds changes to support more customizable input.
The primary target for customization are start and end accessories within the DS Input Component we're using in extension. This PR allows <Box> as the left or right accessory.
Box elements and their children elements are adjacent to the primary Field-compatible child component, just like the support for the <Button> we have from previous implementations.

Related task: https://github.com/MetaMask/MetaMask-planning/issues/3067

Notes:

• This PR does not introduce breaking changes, since possibility for adding just simple plain button to the Input field is still supported.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.31%. Comparing base (5ce5b1d) to head (011016f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2699   +/-   ##
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  Coverage   94.30%   94.31%           
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  Files         481      481           
  Lines       10051    10055    +4     
  Branches     1521     1521           
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+ Hits         9479     9483    +4     
  Misses        572      572           

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