Clarify optional vs. required fields

Added a separator between the fields, and marked required fields as "required", so you can't submit without them

Also - changed from base64 to base58 in for the auto-generated password. It's conceivable that someone might need to read it outloud to someone else - and not having "visually similar" characters (like O and 0) can be helpful.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=228810158

java/google/registry/ui/soy/Forms.soy

@@ -107,6 +107,7 @@
 {template .inputFieldValue}
   {@param name: string}
   {@param? readonly: bool}
+  {@param? required: bool}
   {@param? value: ?}
   {@param? namePrefix: string}
   {@param? placeholder: string}
@@ -119,6 +120,7 @@
          {if isNonnull($placeholder) and not $readonly}
          placeholder="{$placeholder}"
          {/if}
+         {if $required}required{/if}
          {if $readonly}readonly{/if}>
 {/template}
 
@@ -128,6 +130,7 @@
   {@param label: string}
   {@param name: string}
   {@param? readonly: bool}
+  {@param? required: bool}
   {@param? namePrefix: string}
   {@param? value: ?}
   {@param? description: string}