feat(rum-oversight): split draw from loadData

[karlpauls]

Currently, the loadData method is calling draw at the end. This causes some duplicated call to the draw method of the chart - it doesn't really seem to be a performance problem (nor cause other issues) but it seems it would make some sense to move the draw call out of loadData and invoke it explicitly when needed.

Test: https://slicerdraw--helix-website--karlpauls.hlx.page/tools/oversight/explorer.html?domain=aem.live&domainkey=