feat(tools): add 'idf.py qemu' extension

This extension allows running programs in QEMU similar to running
them on a real chip:

- 'idf.py qemu' — builds and runs the program in QEMU. User gets
  a QEMU instance launched, and can work with it as a normal QEMU
  instance.
- 'idf.py qemu monitor' — same, but QEMU is launched in the
  background, and idf_monitor runs in the foreground, showing QEMU
  output. Compared to only running 'idf.py qemu' this enables, for
  example, automatic backtrace decoding.
- 'idf.py qemu gdb' — launches QEMU in the background and opens an
  interactive GDB prompt, connecting it to QEMU.
- 'idf.py qemu --gdb monitor' and 'idf.py gdb' in another shell:
  launches QEMU in the background, keeps it suspended until GDB is
  connected, and opens idf_monitor. GDB can be used in another shell
  to debug the application.

docs/conf_common.py

@@ -145,6 +145,8 @@ ANA_CMPR_DOCS = ['api-reference/peripherals/ana_cmpr.rst']
 
 SPI_SLAVE_HD_DOCS = ['api-reference/peripherals/spi_slave_hd.rst']
 
+QEMU_DOCS = ['api-guides/tools/qemu.rst']
+
 ESP32_DOCS = ['api-reference/system/himem.rst',
               'api-guides/romconsole.rst',
               'api-reference/system/ipc.rst',
@@ -153,7 +155,7 @@ ESP32_DOCS = ['api-reference/system/himem.rst',
               'api-reference/peripherals/dac.rst',
               'api-reference/peripherals/sd_pullup_requirements.rst',
               'hw-reference/esp32/**',
-              'api-guides/RF_calibration.rst'] + FTDI_JTAG_DOCS
+              'api-guides/RF_calibration.rst'] + FTDI_JTAG_DOCS + QEMU_DOCS
 
 ESP32S2_DOCS = ['hw-reference/esp32s2/**',
                 'api-guides/usb-console.rst',
@@ -171,7 +173,7 @@ ESP32S3_DOCS = ['hw-reference/esp32s3/**',
 
 # No JTAG docs for this one as it gets gated on SOC_USB_SERIAL_JTAG_SUPPORTED down below.
 ESP32C3_DOCS = ['hw-reference/esp32c3/**',
-                'api-guides/RF_calibration.rst']
+                'api-guides/RF_calibration.rst'] + QEMU_DOCS
 
 ESP32C2_DOCS = ['api-guides/RF_calibration.rst']