video: truetype: Use pre-allocated buffer for glyph rendering

The TrueType console driver calls malloc/free for every character
rendered, which causes significant memory fragmentation and allocation
traffic.

Add CONFIG_CONSOLE_TRUETYPE_GLYPH_BUF to enable a pre-allocated buffer
in the driver's private data. The buffer starts at 4KB and grows via
realloc() as needed. When rendering a glyph, use this buffer to avoid
malloc/free for normal characters.

The buffer is allocated lazily after relocation to avoid consuming
early malloc space before the full heap is available.

Add CONFIG_VIDEO_GLYPH_STATS (default y on sandbox) to track the number
of glyphs rendered. Use 'font info' to view the count.

Series-changes: 2
- Rename the Kconfig to just enable the feature: always allocate

Co-developed-by: Claude Opus 4 <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>

test/cmd/font.c

@@ -98,3 +98,20 @@ static int font_test_base(struct unit_test_state *uts)
 }
 FONT_TEST(font_test_base, UTF_SCAN_PDATA | UTF_SCAN_FDT | UTF_CONSOLE |
 	  UTF_DM);
+
+/* Test 'font info' command */
+static int font_test_info(struct unit_test_state *uts)
+{
+	int count;
+
+	if (!CONFIG_IS_ENABLED(VIDEO_GLYPH_STATS))
+		return -EAGAIN;
+
+	count = gd_glyph_count();
+	ut_assertok(run_command("font info", 0));
+	ut_assert_nextline("glyphs rendered: %u", count);
+	ut_assert_console_end();
+
+	return 0;
+}
+FONT_TEST(font_test_info, UTF_CONSOLE);