[DOCS] update images

[stufraser1]

After updates to the tool, including branding

• update screenshots in user guide
• add labels onto risk pooling tool image: country 1, 2, 3 etc #52
• update phase 1 and 2 images (step 3 now in phase 2) #53
• update risk pool schematic [DOCS img] risk pool schematic #51

[stufraser1]

Updated main task: images with ecd0062 ; other issues await access to original imagery