EnvironmentWidget: Use HeaderViewStrecher
EnvironmentWidget: Use HeaderViewStrecher

Essentially we use ResizeToContents until the widget is shown to the
user. That is not optimal, since this still can lead to a absurd size
for the keys column, but since the user can then resize it, it is far
better than before. Note: Each hide() + show() will resize the columns
again to their contents.

Task-number: QTCREATORBUG-8982
Change-Id: Iaccd32d4a2ce618a98f9b9d48141fd753c6f8b97
Reviewed-by: Tobias Hunger <012f8d714267bccc9d4766fbeace9f175fcc70c4@digia.com>

darksylinc/qt-creator,AltarBeastiful/qt-creator,darksylinc/qt-creator,amyvmiwei/qt-creator,omniacreator/qtcreator,duythanhphan/qt-creator,farseerri/git_code,xianian/qt-creator,richardmg/qtcreator,farseerri/git_code,maui-packages/qt-creator,xianian/qt-creator,malikcjm/qtcreator,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,Distrotech/qtcreator,AltarBeastiful/qt-creator,AltarBeastiful/qt-creator,martyone/sailfish-qtcreator,kuba1/qtcreator,omniacreator/qtcreator,duythanhphan/qt-creator,omniacreator/qtcreator,xianian/qt-creator,darksylinc/qt-creator,kuba1/qtcreator,duythanhphan/qt-creator,danimo/qt-creator,farseerri/git_code,xianian/qt-creator,darksylinc/qt-creator,colede/qtcreator,richardmg/qtcreator,maui-packages/qt-creator,malikcjm/qtcreator,amyvmiwei/qt-creator,richardmg/qtcreator,colede/qtcreator,omniacreator/qtcreator,malikcjm/qtcreator,maui-packages/qt-creator,kuba1/qtcreator,amyvmiwei/qt-creator,martyone/sailfish-qtcreator,maui-packages/qt-creator,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,colede/qtcreator,martyone/sailfish-qtcreator,danimo/qt-creator,amyvmiwei/qt-creator,AltarBeastiful/qt-creator,danimo/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,malikcjm/qtcreator,farseerri/git_code,maui-packages/qt-creator,kuba1/qtcreator,danimo/qt-creator,xianian/qt-creator,kuba1/qtcreator,kuba1/qtcreator,darksylinc/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,Distrotech/qtcreator,kuba1/qtcreator,danimo/qt-creator,duythanhphan/qt-creator,farseerri/git_code,colede/qtcreator,kuba1/qtcreator,richardmg/qtcreator,omniacreator/qtcreator,danimo/qt-creator,darksylinc/qt-creator,richardmg/qtcreator,Distrotech/qtcreator,colede/qtcreator,maui-packages/qt-creator,Distrotech/qtcreator,farseerri/git_code,malikcjm/qtcreator,Distrotech/qtcreator,omniacreator/qtcreator,AltarBeastiful/qt-creator,duythanhphan/qt-creator,farseerri/git_code,danimo/qt-creator,martyone/sailfish-qtcreator,malikcjm/qtcreator,omniacreator/qtcreator,kuba1/qtcreator,duythanhphan/qt-creator,darksylinc/qt-creator,duythanhphan/qt-creator,maui-packages/qt-creator,martyone/sailfish-qtcreator,farseerri/git_code,darksylinc/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,amyvmiwei/qt-creator,colede/qtcreator,colede/qtcreator,malikcjm/qtcreator,AltarBeastiful/qt-creator,xianian/qt-creator,richardmg/qtcreator,martyone/sailfish-qtcreator,Distrotech/qtcreator,amyvmiwei/qt-creator,danimo/qt-creator,danimo/qt-creator,richardmg/qtcreator,Distrotech/qtcreator