Relative amounts of memory should be visible across memory tracks

When looking at the memory tracks, I find it hard to guess which tracks are relevant because visually I don't have a notion of the relative amounts when comparing memory tracks.

example profile: https://perfht.ml/2WXeT8q

Could we make all the memory tracks of a profile share the same maximum, so that a process allocating 5MB has an almost flat memory track if other processes allocate hundreads of MB at the same time?

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-155)