perf: reduce allocations and optimize hot paths in network simulation

[Copilot]

Identified and fixed several allocation and algorithmic inefficiencies in network packet handling and collection management.

Changes

• Packet segmentation (ip/segments.rs): Eliminated clone on final segment by using Option<Packet> ownership model
• Address hashing (queue/sender.rs): Sized arrays exactly to address type (6 bytes IPv4, 18 bytes IPv6) instead of always allocating 18
• Collection removal (queue/sender.rs): Replaced VecDeque::retain() with position() + remove() for targeted element deletion
• Bitset queries (time/bitset.rs): Changed is_empty() from fold to all() for early-return optimization
• Vector pre-allocation (task/supervisor.rs, pcap/*.rs): Added with_capacity() where size is known upfront

Example: Segment Iterator

Before:

let mut packet = self.packet.clone();  // Clone on every segment
*packet.transport.payload_mut() = payload;

After:

// Take ownership on last segment, clone only intermediate ones
let mut packet = if is_last {
    self.packet.take()?
} else {
    packet.clone()
};

Original prompt

Identify and suggest improvements to slow or inefficient code

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