[Neue] Buttons (#5406)

* Re-align button sizing

(cherry picked from commit bcec243bb59dfe468313d98ba61f464d9750feec)

* Use large, small, tiny

(cherry picked from commit 1dc333c2993ab7f2e0ac750c0670dcec9a7069d0)

* Tweaks

src/screens/Signup/BackNextButtons.tsx

@@ -34,7 +34,7 @@ export function BackNextButtons({
         label={_(msg`Go back to previous step`)}
         variant="solid"
         color="secondary"
-        size="medium"
+        size="large"
         onPress={onBackPress}>
         <ButtonText>
           <Trans>Back</Trans>
@@ -46,7 +46,7 @@ export function BackNextButtons({
             label={_(msg`Press to retry`)}
             variant="solid"
             color="primary"
-            size="medium"
+            size="large"
             onPress={onRetryPress}>
             <ButtonText>
               <Trans>Retry</Trans>
@@ -59,7 +59,7 @@ export function BackNextButtons({
             label={_(msg`Continue to next step`)}
             variant="solid"
             color="primary"
-            size="medium"
+            size="large"
             disabled={isLoading || isNextDisabled}
             onPress={onNextPress}>
             <ButtonText>