Allow user to select specific ESP_TARGET while setting up ESD_IDF.
Only necessary tools for given target will be downloaded and installed.
Closes https://github.com/espressif/esp-idf/issues/5113
When user forgot to add git.exe or python to the PATH, there was a not
very helpful error message.
This improves the error with which tool is misssing and shows a link to
the espressif installer tool.
