feat(server): Memory tracker

[chakaz]

This PR adds AllocationTracker class, which can track (currently print) memory allocations via new and delete based on a given criteria (size & sampling fraction).

As a side effect, now we use mimalloc for new and delete also in debug builds (which wasn't the case before).

Here's the comment above Track(), provided here for completeness:

// Allow tracking of memory allocation via `new` and `delete` based on input criteria.
//
// MEMORY TRACK ADD <lower-bound> <upper-bound> <sample-odds>
// - Sets up tracking memory allocations in the (inclusive) range [lower, upper]
// - sample-odds indicates how many of the allocations will be logged, there 0 means none, 1 means
//   all, and everything in between is linear
// - There could be at most 4 tracking placed in parallel
//
// MEMORY TRACK REMOVE <lower-bound> <upper-bound>
// - Removes all memory tracking added which match bounds
// - Could remove 0, 1 or more
//
// MEMORY TRACK CLEAR
// - Removes all memory tracking
//
// MEMORY TRACK GET
// - Returns an array with all active tracking
//
// This command is not documented in `MEMORY HELP` because it's meant to be used internally.

[chakaz]

This part is a literal cut-paste, no other changes

[romange]

Please add a commit description.

[romange]

is it to prevent a recursive endless loop? care to add a comment?

[romange]

I would put it under core/

[romange]

Can you please introduce a CMakeLists option DFLY_MEMORY_TRACKING in src/CMakelists.txt ?
Let's set it to ON by default and it will add the conditional define to dfly_main.cc.
In case it's disabled we fallback to #include <mimalloc-new-delete.h>

[romange]

ah, I see you add this define to every file but use it only here. ok

[romange]

so we now always allocate via mimalloc. worth adding this to commit description as well.

[romange]

please add comment above how the command looks like:
// MEMORY TRACK ...

[romange]

LGTM!

[romange]

I see.

[chakaz]

🤓