Disable DECKPAM mode behind velocity (#16675)

DECKPAM originally tracked in #16506.
Support was added in #16511.
But turns out people didn't expect the Terminal to actually be like,
compliant: #16654

This closes #16654 while we think over in #16672 how we want to solve
this

(cherry picked from commit 71efdcb)
Service-Card-Id: 91781164
Service-Version: 1.20

Author: zadjii-msft

src/features.xml

@@ -177,4 +177,14 @@
         </alwaysEnabledBrandingTokens>
     </feature>
 
+    <feature>
+        <name>Feature_KeypadModeEnabled</name>
+        <description>Enables the DECKPAM, DECKPNM sequences to work as intended </description>
+        <id>16654</id>
+        <stage>AlwaysDisabled</stage>
+        <alwaysEnabledBrandingTokens>
+            <brandingToken>Dev</brandingToken>
+        </alwaysEnabledBrandingTokens>
+    </feature>
+
 </featureStaging>

src/terminal/input/terminalInput.cpp

@@ -438,7 +438,7 @@ try
         // the ASCII character assigned by the keyboard layout, but when set
         // they transmit SS3 escape sequences. When used with a modifier, the
         // modifier is embedded as a parameter value (not standard).
-        if (_inputMode.test(Mode::Keypad))
+        if (Feature_KeypadModeEnabled::IsEnabled() && _inputMode.test(Mode::Keypad))
         {
             defineNumericKey(VK_MULTIPLY, L'j');
             defineNumericKey(VK_ADD, L'k');
@@ -490,7 +490,7 @@ try
 
         // Keypad keys also depend on Keypad mode, the same as ANSI mappings,
         // but the sequences use an ESC ? prefix instead of SS3.
-        if (_inputMode.test(Mode::Keypad))
+        if (Feature_KeypadModeEnabled::IsEnabled() && _inputMode.test(Mode::Keypad))
         {
             defineKeyWithUnusedModifiers(VK_MULTIPLY, L"\033?j"s);
             defineKeyWithUnusedModifiers(VK_ADD, L"\033?k"s);