fix(seccomp): allow pread64 in VMM thread for Aarch64

[bchalios]

Commit 92eacbd allow-listed calling pread64 from the VMM thread, so that we can read which pages are dirty from the pagemap. But it only did it for x86 architecture.

Allow it also on Aarch64.

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---

• This functionality cannot be added in rust-vmm.

[cursor]

PR Summary

Low Risk
Single syscall allow-list entry in the VMM filter; aligns AArch64 with an existing x86_64 exception and does not broaden API or vCPU filters.

Overview
Adds pread64 to the VMM seccomp allow-list in resources/seccomp/aarch64-unknown-linux-musl.json, with the same rationale as on x86: pagemap reads for dirty-memory tracking during snapshot/diff flows.

This closes an architecture gap where the VMM thread could trap on pread64 on AArch64 builds even though the syscall was already permitted for x86_64.

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