And include a fallback in case we never got an actual Process frame which
will contain the cmdline for the process. We need to hold onto the fallback
too so that we can keep symbols lightweight by not having to reference them
so long as the document is alive.
This internal type is used to collect things about a process like the
memory maps, address layout, and symbol cache. This can persist once
parsed at startup, then applied to objects created on demand such as the
SysprofDocumentProcess or used by symbolizers internally rather than
complicated function arguments.
