Replace getProcessesWithMemoryTrack with more generic approach

#5752 consolidated Memory / Power / Bandwidth / ProcessCPU into a single generic counter track type. However, we still have [getProcessesWithMemoryTrack](https://github.com/firefox-devtools/profiler/blob/main/src/selectors/profile.ts#L550), which hard-codes memory-specific behavior. The selector tells the main thread whether a memory track already exists, so it knows whether to suppress duplicate rendering of the memory markers (we render them on the main thread's marker row, if no memory track exists).

This behavior should be generalized and not hardcoded in the frontend code. Apparently, we should replace the selector with a schema-based approach.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-1263)