Review hybrid Password component decision using Text Input with before/after content

[calvin-lau-sig7]

Decide what will be built for the Password Input component, and how it fits in with other component parts.

Includes: Review putting toggle button in template (vs JavaScript)

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Why

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• Thing to do

[querkmachine]

Given the changes since made to the main branch to make components easier to extend (e.g. #4567, #4742), we're now more comfortable having the Password input component inherit the Input component, rather than implementing it as a separate entity.

This approach was spiked in #4741 and #4746, where we validated that this approach would be practical.