perf: replace system allocator with tikv-jemallocator to reduce contention (or maybe mimalloc)

[carabistouflette]

The project currently uses the default system memory allocator. Generally, when dealing with high-throughput, multithreaded workloads (which Psyche heavily relies on), the system allocator can lead to significant memory fragmentation and lock contention, degrading overall performance.

Rust's default allocator relies on libc's malloc, which is not optimized for the concurrent allocation patterns seen in the heavy async and threaded workloads. jemalloc is an industry standard for such applications (used by TiKV, RocksDB, Redis...) and is known to provide better introspection and performance in these scenarios.

Solution:

Add tikv-jemallocator to

architectures/decentralized/solana-client/Cargo.toml

Register TikvJemallocator as the global allocator in

architectures/decentralized/solana-client/src/main.rs

[carabistouflette]

It seems to be also used by the official Solana validator. Seems fair to add it.