Remove Prices from UI for Testnets

[fubuloubu]

This isn't really useful information on testnets, and it would create an additional UX feedback if the monetary value only appeared on networks where the tokens had value.

A naive suggestion would just be to hide it using the network selector. Something better would be to change the positions of the amount of ETH you have to fill in the negative space left by removing the price.

[wbt]

Allowing someone to specify a different lookup / fiat conversion service per network would be a good solution here, including an option to leave the field blank, in which case no conversion is shown.

[bdresser]

Agreed @fubuloubu, and we've received some feedback that it's actually confusing to include the conversion on testnets.

Also agree it'd be nice to allow a conversion on custom networks if the user wants @wbt.

• Hide conversion by default for all testnets
• Add a toggle to settings for "show conversion on test networks" (defaulted to "off")
• Update the Custom RPC form in settings to include a conversion drop-down, defaulted to "None." (See mock-up below)
• We really need to clean up the settings menu :) Organize Settings Menu #5790

cc @omnat @cjeria

[fubuloubu]

Nice! I actually could see the price thing being opt-out instead of opt-in. I definitely see the argument for new users to impress on them the costs of using applications as UX feedback preparing them for mainnet, I just want to be able to shut it off as a power user.

[bdresser]

We've heard feedback from novice users that it can make using testnets feel scary. @omnat will probably do a little more research before we make a change here.

[wbt]

I've also gotten user feedback about how confusing it is on private networks. Instead of differentiating between public testnets and others with a particular setting, I propose we treat all networks the same from the perspective of settings.
The main network gets a default value matching the currency conversion service currently in place, but the user should be able to (a) change this to another service [which might track prices from a different source, for example], and (b) easily copy the setting and paste it in to the test network settings. We can debate whether or not to have the same value used by default for the public test networks.
We could add a boolean/checkbox field under currency conversion "Show as test" enabled true by default for the big public test networks which would cause the currency conversion to show up differently: maybe a different color, or in parentheses, with explanatory text or hovertext.