network difficulty graph improvements - monero axis label and scale

[delta1]

On the network difficulty graph, the Monero difficulty should have its own y-axis label on the right side, and be scaled appropriately to look better with the Tari difficulty. The x-axis should also be reversed, to increase from left to right.

For example: in the screenshot the Monero difficulty is 9647, while the Tari difficulty is > 2 billion. So the y-axis on the right could go up to 10 000.

A legend should be shown underneath the chart showing: "RandomX (Merge mined)" and "SHA3" for the series.

When hovering, the label on the chart should display:
For RandomX (example values)

Block: 9647
RandomX: 2b

For SHA3 (example values)

Block: 9646
SHA3: 2b