This updates all Rc that were ignored for malloc_size_of to use
conditional_malloc_size_of, unless the type in the Rc itself doesn't
support malloc_size.
Regular expressions used to search for all occurrences:
```
ignore_malloc_size_of = "Rc.*"
ignore_malloc_size_of = "Arc.*"
```
There are a couple left since they have nested Rc, which I don't know
how to fix.
To be able to define these, several new implementations were added to
`malloc_size_of/lib.rs` as well as
`HashMapTracedValues`.
Testing: if it compiles, it's safe
Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>
