fix: limit reification sizes

[vyzo]

It was observed that during sync from snapshot some very large reification walks would trigger, consuming excessive memory.

This introduces a limit to reification mass, and aborts if the visited object count is exceeded.

[vyzo]

Note that this also makes the in-memory visitors smarter so as to not waste memory on unitary objects that are not walked anyway.

[codecov]

Codecov Report

Merging #8149 (a7b1d86) into master (cf7a041) will decrease coverage by 0.02%.
The diff coverage is 63.63%.

@@            Coverage Diff             @@
##           master    #8149      +/-   ##
==========================================
- Coverage   39.51%   39.48%   -0.03%     
==========================================
  Files         666      666              
  Lines       72498    72507       +9     
==========================================
- Hits        28646    28632      -14     
- Misses      38902    38913      +11     
- Partials     4950     4962      +12     

Impacted Files	Coverage Δ
blockstore/splitstore/visitor.go	75.00% <0.00%> (-25.00%)	⬇️
blockstore/splitstore/splitstore_reify.go	55.37% <100.00%> (+4.50%)	⬆️
cli/util.go	41.66% <0.00%> (-8.34%)	⬇️
storage/wdpost_sched.go	77.45% <0.00%> (-7.85%)	⬇️
chain/exchange/peer_tracker.go	66.66% <0.00%> (-4.31%)	⬇️
chain/stmgr/call.go	71.51% <0.00%> (-3.64%)	⬇️
extern/storage-sealing/fsm.go	56.44% <0.00%> (-2.44%)	⬇️
extern/sector-storage/sched.go	83.12% <0.00%> (-1.65%)	⬇️
chain/stmgr/searchwait.go	67.30% <0.00%> (-1.29%)	⬇️
storage/wdpost_changehandler.go	97.64% <0.00%> (-0.95%)	⬇️
... and 15 more

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[jennijuju]

please update the pr title according to the instructions in PR template.