esp_lcd_qemu_rgb minor fixes

[igrr]

This PR has small fixes for esp_lcd_qemu_rgb:

• Fixed compatibility with IDF v5.3-dev. In IDF commit ad84b61e490cf1671984e7a52997d5011c5eb7be (MR 28412), esp_lcd_panel_rgb.h is made available only for chip targets with LCD_CAM peripheral. Fix the example project to not include this header, since it's not needed anyway
• Switched the example to use the 16-bit color format introduced in #287. This makes it one less setting to keep in mind, and closer to what most people are going to use.
• Updated the changelog.

[github-actions[bot]]

Unit Test Results

  15 files    15 suites   21m 8s :stopwatch:   27 tests   27 :heavy_check_mark: 0 :zzz: 0 :x: 382 runs  382 :heavy_check_mark: 0 :zzz: 0 :x:

Results for commit d960ff18.

:recycle: This comment has been updated with latest results.