Deprecate UiTokenAmount::ui_amount (#15616)

* Add TokenAmount::ui_amount_string

* Fixup solana-tokens

* Update docs

tokens/src/token_display.rs

@@ -1,4 +1,4 @@
-use solana_account_decoder::parse_token::token_amount_to_ui_amount;
+use solana_account_decoder::parse_token::real_number_string_trimmed;
 use solana_sdk::native_token::lamports_to_sol;
 use std::{
     fmt::{Debug, Display, Formatter, Result},
@@ -27,7 +27,7 @@ impl Token {
                 write!(f, "{}{}", SOL_SYMBOL, amount)
             }
             TokenType::SplToken => {
-                let amount = token_amount_to_ui_amount(self.amount, self.decimals).ui_amount;
+                let amount = real_number_string_trimmed(self.amount, self.decimals);
                 write!(f, "{} tokens", amount)
             }
         }