Interlock `inflated_signatures_size`, `memberref_sig_cache_size`, `methods_size` and `signatures_size` (#5489)
[TSan] Interlocking loader.c
`loader.c` contains four statistics counters and all of them are invovled in data races. This PR focuses on dealing with them:
- All of them can be `gint32` as they are registered as `MONO_COUNTER_INT` anyways.
- Since there is already a lot of locking involved in `loader.c` (including an approved usage of `Interlocked* ()` with with `mono_stats`), I think that `Interlocked* ()` can be used here instead of `Unlocked* ()`. If this assumption is wrong, I would kindly ask to correct me by commenting the affected rows and I will change it to `Unlocked* ()`.