Fix VtEngine hang when resizing while scrolling (#15618)

This fixes a bug reported internally that occurs when resizing the
terminal while also scolling the contents. The easiest way to reproduce
it is to resize the terminal to 0 rows, but it's much more prominent
in a debug build where everything goes out of sync almost immediately.

The underlying issue is that `VtEngine::_wrappedRow` may contain an
offset that is outside of the viewport bounds, because reflowing and
scrolling aren't properly synchronized. The previous `bitmap` code
would then throw an exception for such invalid coordinates and cause
the internal `VtEngine` state to be broken. Once `_wrappedRow` got
to a negative value at least once, it would stay that way unless you're
scrolling up. If the contents are actively scrolling it would quickly
reach a negative value from which it can never recover. At that point
OpenConsole would enter a tight exception-throw-catch-retry loop
and Windows Terminal seemingly cease to show any content.

## Validation Steps Performed
* Resize WT to the minimal window size repeatedly
* Doesn't hang ✅

src/inc/til/bitmap.h

@@ -351,20 +351,26 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
 
             void set(const til::point pt)
             {
-                THROW_HR_IF(E_INVALIDARG, !_rc.contains(pt));
-                _runs.reset(); // reset cached runs on any non-const method
-
-                _bits.set(_rc.index_of(pt));
+                if (_rc.contains(pt))
+                {
+                    _runs.reset(); // reset cached runs on any non-const method
+                    _bits.set(_rc.index_of(pt));
+                }
             }
 
-            void set(const til::rect& rc)
+            void set(til::rect rc)
             {
-                THROW_HR_IF(E_INVALIDARG, !_rc.contains(rc));
                 _runs.reset(); // reset cached runs on any non-const method
 
-                for (auto row = rc.top; row < rc.bottom; ++row)
+                rc &= _rc;
+
+                const auto width = rc.width();
+                const auto stride = _rc.width();
+                auto idx = _rc.index_of({ rc.left, rc.top });
+
+                for (auto row = rc.top; row < rc.bottom; ++row, idx += stride)
                 {
-                    _bits.set(_rc.index_of(til::point{ rc.left, row }), rc.width(), true);
+                    _bits.set(idx, width, true);
                 }
             }
 

src/til/ut_til/BitmapTests.cpp

@@ -632,26 +632,19 @@ class BitmapTests
         _checkBits(expectedSet, bitmap);
     }
 
-    TEST_METHOD(SetResetExceptions)
+    TEST_METHOD(SetResetOutOfBounds)
     {
         til::bitmap map{ til::size{ 4, 4 } };
         Log::Comment(L"1.) SetPoint out of bounds.");
-        {
-            auto fn = [&]() {
-                map.set(til::point{ 10, 10 });
-            };
-
-            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_INVALIDARG; });
-        }
+        map.set(til::point{ 10, 10 });
 
         Log::Comment(L"2.) SetRectangle out of bounds.");
-        {
-            auto fn = [&]() {
-                map.set(til::rect{ til::point{ 2, 2 }, til::size{ 10, 10 } });
-            };
+        map.set(til::rect{ til::point{ 2, 2 }, til::size{ 10, 10 } });
 
-            VERIFY_THROWS_SPECIFIC(fn(), wil::ResultException, [](wil::ResultException& e) { return e.GetErrorCode() == E_INVALIDARG; });
-        }
+        const auto runs = map.runs();
+        VERIFY_ARE_EQUAL(2u, runs.size());
+        VERIFY_ARE_EQUAL(til::rect(2, 2, 4, 3), runs[0]);
+        VERIFY_ARE_EQUAL(til::rect(2, 3, 4, 4), runs[1]);
     }
 
     TEST_METHOD(Resize)