Implicit SHM optimization

[yellowhatter]

• adds implicit SHM opt: implicitly pack big slices into SHM buffers. This is true for any operation mode incl. Router - so zenohd will be able to distribute network data as SHM locally
• optimize different transport objects layouts so that transport is getting more cache-friendly (adds ~500k for both SHM and non-SHM compiled binaries)

[yellowhatter]

The CI issues are upstream and not related to this PR

[codecov]

Codecov Report

❌ Patch coverage is 94.33198% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.90%. Comparing base (b1a5745) to head (808460a).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
io/zenoh-transport/src/shm.rs	90.81%	9 Missing ⚠️
io/zenoh-transport/src/multicast/establishment.rs	90.00%	1 Missing ⚠️
io/zenoh-transport/src/shm_context.rs	97.43%	1 Missing ⚠️
io/zenoh-transport/src/unicast/lowlatency/rx.rs	66.66%	1 Missing ⚠️
io/zenoh-transport/src/unicast/manager.rs	92.85%	1 Missing ⚠️
io/zenoh-transport/src/unicast/universal/tx.rs	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2113      +/-   ##
==========================================
+ Coverage   70.78%   70.90%   +0.12%     
==========================================
  Files         372      373       +1     
  Lines       63024    63157     +133     
==========================================
+ Hits        44609    44780     +171     
+ Misses      18415    18377      -38     

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