Fix a hang when writing wide glyphs into a 1 column terminal (#15171)

The code changes are mostly self-explanatory: Just skip glyphs
that can never be inserted. I implemented it slightly incorrectly
(a newline will be inserted every time you write such a wide glyph),
but it's a niche issue and I think the simplicity of the fix is
more important than its exact correctness.

It also contains a fix for some severe log spam due to
`_PrepareForDoubleByteSequence` complaining in this situation.
The spam is so bad that it freezes the app for a few seconds
during text buffer reflow.

Closes #7416

## Validation Steps Performed
* Open an extra pane and run `TerminalStress.exe` in there
* Resize to 1 column
* Doesn't hang ✅

src/buffer/out/textBuffer.cpp

@@ -272,10 +272,6 @@ bool TextBuffer::_AssertValidDoubleByteSequence(const DbcsAttribute dbcsAttribut
 // - false otherwise (out of memory)
 bool TextBuffer::_PrepareForDoubleByteSequence(const DbcsAttribute dbcsAttribute)
 {
-    // This function corrects most errors. If this is false, we had an uncorrectable one which
-    // older versions of conhost simply let pass by unflinching.
-    LOG_HR_IF(E_NOT_VALID_STATE, !(_AssertValidDoubleByteSequence(dbcsAttribute))); // Shouldn't be uncorrectable sequences unless something is very wrong.
-
     auto fSuccess = true;
     // Now compensate if we don't have enough space for the upcoming double byte sequence
     // We only need to compensate for leading bytes

src/terminal/adapter/adaptDispatch.cpp

@@ -139,18 +139,26 @@ void AdaptDispatch::_WriteToBuffer(const std::wstring_view string)
 
         if (isWrapping)
         {
+            // We want to wrap, but we failed to write even a single character into the row.
+            // ROW::Write() returns the lineWidth and leaves stringIterator untouched. To prevent a
+            // deadlock, because stringIterator never advances, we need to throw that glyph away.
+            //
+            // This can happen under two circumstances:
+            // * The glyph is wider than the buffer and can never be inserted in
+            //   the first place. There's no good way to detect this, so we check
+            //   whether the begin column is the left margin, which is the column
+            //   at which any legit insertion should work at a minimum.
+            // * The DECAWM Autowrap mode is disabled ("\x1b[?7l", !wrapAtEOL) and
+            //   we tried writing a wide glyph into the last column which can't work.
+            if (textPositionBefore == textPositionAfter && (state.columnBegin == 0 || !wrapAtEOL))
+            {
+                textBuffer.ConsumeGrapheme(state.text);
+            }
+
             if (wrapAtEOL)
             {
                 cursor.DelayEOLWrap();
             }
-            else if (textPositionBefore == textPositionAfter)
-            {
-                // We want to wrap, but we're not allowed to and we failed to write even a single character into the row.
-                // This can only mean one thing! The DECAWM Autowrap mode is disabled ("\x1b[?7l") and we tried writing a
-                // wide glyph into the last column. ROW::Write() returns the lineWidth and leaves stringIterator untouched.
-                // To prevent a deadlock, because stringIterator never advances, we need to throw that glyph away.
-                textBuffer.ConsumeGrapheme(state.text);
-            }
         }
     }