refacto: Create method to get Token value instead of repeating find

[vprothais]

The following code is used very often : allTokens.find((token) => token.name === '$ouds-xxx').compiledValue.

We could enhance the readability by defining a function getTokenValue(tokenName) or equivalent in the sass-variables file, that just get the token name as a parameter and return the compiledValue.

Originally posted by @vprothais in #3181 (comment)