Use Terminal.readSecret in add string keystore command

As a followon to elastic#126729, the add string keystore command doesn't need
to use a reader at all (and it was incorrect for it to close the reader
from the terminal). Instead, the Terminal abstraction already handles
how to get at line by line secrets. This commit removes that usage of
reader and uses readSecret calls instead.

closes elastic#126882

Author: rjernst

distribution/tools/keystore-cli/src/main/java/org/elasticsearch/cli/keystore/AddStringKeyStoreCommand.java

@@ -53,42 +53,26 @@ protected void executeCommand(Terminal terminal, OptionSet options, Environment
 
         final KeyStoreWrapper keyStore = getKeyStore();
 
-        final Closeable closeable;
-        final CheckedFunction<String, char[], IOException> valueSupplier;
-        if (options.has(stdinOption)) {
-            final Reader stdinReader = terminal.getReader();
-            valueSupplier = s -> {
-                try (CharArrayWriter writer = new CharArrayWriter()) {
-                    int c;
-                    while ((c = stdinReader.read()) != -1) {
-                        if ((char) c == '\r' || (char) c == '\n') {
-                            break;
-                        }
-                        writer.write((char) c);
-                    }
-                    return writer.toCharArray();
-                }
-            };
-            closeable = stdinReader;
-        } else {
-            valueSupplier = s -> terminal.readSecret("Enter value for " + s + ": ");
-            closeable = () -> {};
-        }
-
-        try (closeable) {
-            for (final String setting : settings) {
-                if (keyStore.getSettingNames().contains(setting) && options.has(forceOption) == false) {
-                    if (terminal.promptYesNo("Setting " + setting + " already exists. Overwrite?", false) == false) {
-                        terminal.println("Exiting without modifying keystore.");
-                        return;
-                    }
+        final CheckedFunction<String, char[], IOException> valueSupplier = s -> {
+            String prompt = "";
+            if (options.has(stdinOption) == false) {
+                prompt = "Enter value for " + s + ": ";
+            }
+            return terminal.readSecret(prompt);
+        };
+        
+        for (final String setting : settings) {
+            if (keyStore.getSettingNames().contains(setting) && options.has(forceOption) == false) {
+                if (terminal.promptYesNo("Setting " + setting + " already exists. Overwrite?", false) == false) {
+                    terminal.println("Exiting without modifying keystore.");
+                    return;
                 }
+            }
 
-                try {
-                    keyStore.setString(setting, valueSupplier.apply(setting));
-                } catch (final IllegalArgumentException e) {
-                    throw new UserException(ExitCodes.DATA_ERROR, e.getMessage());
-                }
+            try {
+                keyStore.setString(setting, valueSupplier.apply(setting));
+            } catch (final IllegalArgumentException e) {
+                throw new UserException(ExitCodes.DATA_ERROR, e.getMessage());
             }
         }