Replacing existing browser tree node png icons with the svg icons. Made

it compatible with the pgAdmin 4 color combination.

TODO::
Icons for the following nodes are in PNG format.
- Domain Constraint (Only the invalid icon)
- pgAgent Job Steps
- Green Plum database server
- Server (Only server.png, which is used in the create/edit dialog)

web/pgadmin/browser/server_groups/static/img/server_group.svg

@@ -0,0 +1 @@
+<svg id="Layer_1" data-name="Layer 1" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><defs><style>.cls-1{fill:#def4fd;}.cls-2,.cls-3{fill:#2980b9;}.cls-3{stroke:#2980b9;stroke-miterlimit:1;stroke-width:0.5px;}</style></defs><title>server_group</title><path class="cls-1" d="M2.2,2.1H9.8a1.13,1.13,0,0,1,1.13,1.13v.85A1.13,1.13,0,0,1,9.8,5.2H2.2A1.13,1.13,0,0,1,1.08,4.08V3.23A1.12,1.12,0,0,1,2.2,2.1Z"/><path class="cls-2" d="M9.8,2.47a.75.75,0,0,1,.75.75v.85a.75.75,0,0,1-.75.75H2.2a.75.75,0,0,1-.75-.75V3.22a.75.75,0,0,1,.75-.75H9.8m0-.75H2.2A1.5,1.5,0,0,0,.7,3.22v.85a1.5,1.5,0,0,0,1.5,1.5H9.8a1.5,1.5,0,0,0,1.5-1.5V3.22a1.5,1.5,0,0,0-1.5-1.5Z"/><line class="cls-3" x1="4.38" y1="3.65" x2="2.27" y2="3.65"/><path class="cls-1" d="M2.2,6H9.8a1.13,1.13,0,0,1,1.13,1.13v.85A1.12,1.12,0,0,1,9.8,9H2.2A1.12,1.12,0,0,1,1.08,7.92V7.08A1.12,1.12,0,0,1,2.2,6Z"/><path class="cls-2" d="M9.8,6.32a.75.75,0,0,1,.75.75v.85a.75.75,0,0,1-.75.75H2.2a.75.75,0,0,1-.75-.75V7.07a.75.75,0,0,1,.75-.75H9.8m0-.75H2.2A1.5,1.5,0,0,0,.7,7.07v.85a1.5,1.5,0,0,0,1.5,1.5H9.8a1.5,1.5,0,0,0,1.5-1.5V7.07a1.5,1.5,0,0,0-1.5-1.5Z"/><line class="cls-3" x1="4.38" y1="7.5" x2="2.27" y2="7.5"/><path class="cls-1" d="M2.2,9.8H9.8a1.12,1.12,0,0,1,1.12,1.12v.85A1.13,1.13,0,0,1,9.8,12.9H2.2a1.12,1.12,0,0,1-1.12-1.12v-.85A1.13,1.13,0,0,1,2.2,9.8Z"/><path class="cls-2" d="M9.8,10.18a.75.75,0,0,1,.75.75v.85a.75.75,0,0,1-.75.75H2.2a.75.75,0,0,1-.75-.75v-.85a.75.75,0,0,1,.75-.75H9.8m0-.75H2.2a1.5,1.5,0,0,0-1.5,1.5v.85a1.5,1.5,0,0,0,1.5,1.5H9.8a1.5,1.5,0,0,0,1.5-1.5v-.85a1.5,1.5,0,0,0-1.5-1.5Z"/><line class="cls-3" x1="4.38" y1="11.35" x2="2.27" y2="11.35"/></svg>