Docs do not use consistent UI element syntax [all sections except Node Operators]

[barriebyron]

To achieve a consistent structure, output, and tone, we want our technical content to use a standard syntax for UI elements.

We have various inconsistent syntax now, so remove double quotations, italics, and other various syntax and apply bold to UI elements:

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Consistent Markdown syntax and style guidance is provided in UI elements and interaction in the Google developer documentation style guide.

Let's talk about possibly including all syntax for how things look. For example, we want to remove bold around new term introductions, like **Ouroboros Samasika** in Consensus.

We don't have many UI elements in the documentation, so this issue covers all docs sections except the Node Operator-related sections that are undergoing improvement separately. We will also want to address tense in the content there eventually but now is not the time.