RTT initialization bug fixes

Add a setting toggle to enable/disable RTT
Allow calls to be initiated with RTT enabled (add plumbing)
Refactor to match the change to dial()

Bug: 71873552
Test: manual
Change-Id: I79b415751b7f1495a3cd603b83f8c4df4389c4c8
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 7d662f5..2fb1ef7 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -1169,6 +1169,11 @@
     <string name="hac_mode_title">Hearing aids</string>
     <string name="hac_mode_summary">Turn on hearing aid compatibility</string>
 
+    <!-- RTT settings: used to turn on/off Real-Time Text, an accessibility feature similar to
+         TTY that allows users to send text over a phone call. -->
+    <string name="rtt_mode_title">RTT</string>
+    <string name="rtt_mode_summary">Turn RTT on or off</string>
+
     <!-- Service option entries.  -->
     <string-array name="tty_mode_entries">
         <item>TTY Off</item>