Enable module API SendClusterMessage to use light message header type

[hpatro]

This change uses the light message header for cluster module message type to be sent to a target node or broadcast across the cluster. The light message header was introduced in Valkey 8 to reduce network in/out over clusterbus and have been already used for pub/sub message transfer. It's only used if the target node supports the light message header (~30B) otherwise it falls back to using the regular header (~2KB). The module API VM_SendClusterMessage remains as is.

[hpatro]

This helps simplify the code a bit however it's just iterating over one node.

[codecov]

Codecov Report

Attention: Patch coverage is 18.75000% with 52 lines in your changes missing coverage. Please review.

Project coverage is 70.94%. Comparing base (87cc3d7) to head (5322d99).
Report is 1 commits behind head on unstable.

Files with missing lines	Patch %	Lines
src/cluster_legacy.c	18.75%	52 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #1572      +/-   ##
============================================
- Coverage     70.94%   70.94%   -0.01%     
============================================
  Files           121      121              
  Lines         65130    65181      +51     
============================================
+ Hits          46208    46240      +32     
- Misses        18922    18941      +19     

Files with missing lines	Coverage Δ
src/module.c	9.60% <ø> (ø)
src/cluster_legacy.c	86.22% <18.75%> (-0.97%)	⬇️

... and 11 files with indirect coverage changes

[zuiderkwast]

It looks pretty good, but we need cross-version testing IMO with a mixed cluster to make sure it works during rolling upgrade, i.e. a mixed cluster. Can you take my work from #1371 and add it here? Or help completing it.

[sarthakaggarwal97]

Can you take my work from #1371 and add it here? Or help completing it.

@zuiderkwast just out of curiosity what is pending over here? I see @madolson approved the PR as well. I can help contribute / complete it.