Profiles heatmap

I propose the addition of a profiles heatmap alongside the current time-series visualization for profiling data.

(_this is how it looked in Pyroscope cloud_)

In this representation:

Each cell corresponds to a group of profiles meeting the XY criteria:
- X: Time range
- Y: Sum of sample values per profile (illustrated as CPU seconds in the example)

Z axis is encoded in color and indicates the number of profiles in the cell (normalised)

Users should be able to select specific areas on the heatmap and visualize the profiling data for the chosen cell or region. Additionally, the feature should support the comparison or differentiation of selected areas.