[textinput] Do not assign ESC a special meaning on history search mode

UNIX terminals, e.g. vt100, send escape sequences for many special
key combinations. Entering the history search mode assigned a specific
meaning to the ESC character and disabled the processing of escape
sequences, thus accidentally printing some characters that are part
of a CSI.

As a workaround, avoid changing the meaning of ESC; users can still
use the well-known `ESC ESC` sequence (or any other editor command,
e.g. move left/right) to exit the history search mode.

This change only affects UNIX terminals.

Closes issue root-project#10209.

core/textinput/src/textinput/Editor.cpp

@@ -152,7 +152,6 @@ namespace textinput {
     // Stop incremental history search, leaving text at the
     // history line currently selected.
     if (fMode == kInputMode) return;
-    fContext->GetKeyBinding()->EnableEscCmd(false);
     SetEditorPrompt(Text());
     DisplayR.ExtendPromptUpdate(Range::kUpdateEditorPrompt);
     fMode = kInputMode;
@@ -461,7 +460,6 @@ namespace textinput {
         fSearch.clear();
         fMode = (M == kCmdReverseSearch ? kHistRevSearchMode : kHistFwdSearchMode);
         SetHistSearchModePrompt(R.fDisplay);
-        fContext->GetKeyBinding()->EnableEscCmd(true);
         if (UpdateHistSearch(R)) return kPRSuccess;
         return kPRError;
       case kCmdHistReplay: