feat(simulator): implement PacketSimulator for deterministic simulator

[krishvishal]

Summary:

• Adds a PacketSimulator that models a full network fault-injection layer: per-path latency (exponential distribution), packet loss, link capacity limits with random eviction, automatic network partitioning with configurable lifecycle, and per-path clogging.
• Adds a ReadyQueue — a min-heap priority queue with reservoir-sampled random ready removal, used to order packets by delivery tick and uniformly select among simultaneously ready items.
• Partition modes: UniformSize, UniformPartition, IsolateSingle, all guarantee at least one node in each partition. Supports symmetric and asymmetric partitions.

Note:

• Pull-based batch delivery: step() returns all ready packets for the current tick in a single Vec. Packets delivered in the same tick cannot trigger chain reactions within
  that tick. This was done because its difficult to do self-referential structs in Rust and even with using dynamic dispatch we have to fight the borrow checker since we would need mutable access to different fields at the same time.

[codecov]

Codecov Report

❌ Patch coverage is 72.67525% with 191 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.63%. Comparing base (6f01169) to head (1e9caf7).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
core/simulator/src/packet.rs	79.13%	103 Missing and 3 partials ⚠️
core/simulator/src/network.rs	0.00%	55 Missing ⚠️
core/simulator/src/ready_queue.rs	77.94%	24 Missing and 6 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2769      +/-   ##
============================================
+ Coverage     67.58%   67.63%   +0.05%     
  Complexity      708      708              
============================================
  Files          1027     1030       +3     
  Lines         83147    83846     +699     
  Branches      60004    60714     +710     
============================================
+ Hits          56195    56711     +516     
- Misses        24612    24775     +163     
- Partials       2340     2360      +20     

Flag	Coverage Δ
csharp	67.06% <ø> (-0.19%)	⬇️
go	6.84% <ø> (ø)
java	54.02% <ø> (ø)
node	92.26% <ø> (-0.07%)	⬇️
python	0.00% <ø> (ø)
rust	69.69% <72.67%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
core/common/src/types/consensus/header.rs	13.97% <ø> (ø)
core/simulator/src/lib.rs	0.00% <ø> (ø)
core/simulator/src/ready_queue.rs	77.94% <77.94%> (ø)
core/simulator/src/network.rs	0.00% <0.00%> (ø)
core/simulator/src/packet.rs	79.13% <79.13%> (ø)

... and 13 files with indirect coverage changes

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[krishvishal]

I think both of these are flaky integration tests.

• integration::mod cli::personal_access_token::test_pat_login_options::should_be_successful
• integration::mod cli::system::test_cli_session_scenario::should_be_successful