Upgrade mimalloc to v2.2.7 and log active memory allocator (#876)

- Upgrade mimalloc from v2.1.2 to v2.2.7. Note that mimalloc is no longer the default allocator so this only impacts users who somehow opt into mimalloc via `--malloc=mimalloc` or compile with different defaults
- Add all available mimalloc versions (1.6.7–3.2.8) to the package definition for testing
- Log the active memory allocator (with version where available) at server startup
- Annotate vendored rpmalloc with its source commit and version

## Notable changes in mimalloc 2.1.2 → 2.2.7

- **Memory release fix** (2.2.4): fix case where OS memory was not always fully released
- **Race condition fix** (2.2.6): fixed rare race condition and potential buffer overflow in debug statistics
- **Windows arm64 support** (2.1.9)
- **Guarded build** (2.1.9): new build mode that places OS guard pages behind objects to catch buffer overflows
- **THP awareness** (2.2.6): auto-detects transparent huge pages and adjusts purge size to avoid fragmentation
- **Faster TLS access on Windows** (2.2.6)
- **Improved calloc and aligned allocation performance** (2.2.6)
- **New diagnostic APIs** (2.2.2): `mi_options_print`, `mi_arenas_print`, `mi_stat_get` / `mi_stat_get_json`
- **macOS**: use `MADV_FREE_REUSABLE` for better memory behavior (2.2.4)
- **Build fixes**: Android, Xbox, musl, mingw, arm32, Debian 32-bit, non-BMI1 x64 systems

## Allocator logging

Added `FMalloc::GetName()` pure virtual so the server logs which allocator is active at startup:
```
zenserver - memory allocator: mimalloc 2.2.7
```

Allocator names include version where available:
- `mimalloc 2.2.7` (runtime version via `mi_version()`)
- `rpmalloc 1.5.0-dev.20250810` (ad-hoc version from vendored develop branch commit)
- `ansi`, `stomp` (no version info available)

## Test plan

- [x] Builds successfully on Windows (release)
- [x] Verify server startup log shows allocator name
- [x] Test with `--malloc=mimalloc` (default) and `--malloc=rpmalloc`
- [x] Run test suites to check for regressions

5 files changed, 32 insertions, 2 deletions

diff --git a/src/zencore/memory/fmalloc.cpp b/src/zencore/memory/fmalloc.cpp
index 3e96003f5..b64fe1f2e 100644
--- a/src/zencore/memory/fmalloc.cpp
+++ b/src/zencore/memory/fmalloc.cpp
@@ -56,8 +56,9 @@ class FInitialMalloc : public FMalloc
 		Memory::Initialize();
 		return GMalloc->GetAllocationSize(Original, SizeOut);
 	}
-	virtual void OnMallocInitialized() override {}
-	virtual void Trim(bool bTrimThreadCaches) override { ZEN_UNUSED(bTrimThreadCaches); }
+	virtual void		OnMallocInitialized() override {}
+	virtual void		Trim(bool bTrimThreadCaches) override { ZEN_UNUSED(bTrimThreadCaches); }
+	virtual const char* GetName() const override { return "initial"; }
 } GInitialMalloc;
 
 FMalloc* GMalloc = &GInitialMalloc; /* Memory allocator */
diff --git a/src/zencore/memory/mallocansi.cpp b/src/zencore/memory/mallocansi.cpp
index 9c3936172..e9465b46b 100644
--- a/src/zencore/memory/mallocansi.cpp
+++ b/src/zencore/memory/mallocansi.cpp
@@ -248,4 +248,10 @@ FMallocAnsi::GetAllocationSize(void* Original, size_t& SizeOut)
 #endif
 }
 
+const char*
+FMallocAnsi::GetName() const
+{
+	return "ansi";
+}
+
 }  // namespace zen
diff --git a/src/zencore/memory/mallocmimalloc.cpp b/src/zencore/memory/mallocmimalloc.cpp
index 1f9aff404..1679eebde 100644
--- a/src/zencore/memory/mallocmimalloc.cpp
+++ b/src/zencore/memory/mallocmimalloc.cpp
@@ -191,6 +191,18 @@ FMallocMimalloc::Trim(bool bTrimThreadCaches)
 	mi_collect(bTrimThreadCaches);
 }
 
+const char*
+FMallocMimalloc::GetName() const
+{
+	static char Name[32] = {};
+	if (Name[0] == '\0')
+	{
+		int Ver = mi_version();
+		snprintf(Name, sizeof(Name), "mimalloc %d.%d.%d", Ver / 100, (Ver / 10) % 10, Ver % 10);
+	}
+	return Name;
+}
+
 #	undef DEBUG_FILL_FREED
 #	undef DEBUG_FILL_NEW
 
diff --git a/src/zencore/memory/mallocrpmalloc.cpp b/src/zencore/memory/mallocrpmalloc.cpp
index c45186b77..6c7bfe4f5 100644
--- a/src/zencore/memory/mallocrpmalloc.cpp
+++ b/src/zencore/memory/mallocrpmalloc.cpp
@@ -186,5 +186,10 @@ FMallocRpmalloc::Trim(bool bTrimThreadCaches)
 {
 	ZEN_UNUSED(bTrimThreadCaches);
 }
+const char*
+FMallocRpmalloc::GetName() const
+{
+	return "rpmalloc 1.5.0-dev.20250810";
+}
 }  // namespace zen
 #endif
diff --git a/src/zencore/memory/mallocstomp.cpp b/src/zencore/memory/mallocstomp.cpp
index db9e1535e..54153cbd4 100644
--- a/src/zencore/memory/mallocstomp.cpp
+++ b/src/zencore/memory/mallocstomp.cpp
@@ -278,6 +278,12 @@ FMallocStomp::GetAllocationSize(void* Original, size_t& SizeOut)
 	return true;
 }
 
+const char*
+FMallocStomp::GetName() const
+{
+	return "stomp";
+}
+
 }  // namespace zen
 
 #endif	// WITH_MALLOC_STOMP