SS Only Write Leaf Nodes

[Kbhat1]

Describe your changes and provide context

• Only write iavl leaf nodes to ss during initial sc migration
• This was removed previously incorrectly

Testing performed to validate your change

• Testing on rpc migration node

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 54.89%. Comparing base (d3830c1) to head (4b42148).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
storev2/rootmulti/store.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #548   +/-   ##
=======================================
  Coverage   54.89%   54.89%           
=======================================
  Files         631      631           
  Lines       54954    54954           
=======================================
+ Hits        30165    30166    +1     
+ Misses      22631    22630    -1     
  Partials     2158     2158           

Files with missing lines	Coverage Δ
storev2/rootmulti/store.go	2.60% <0.00%> (ø)

... and 1 file with indirect coverage changes