refactor(rpc): move sanity check logic from rpc handlers to implementations.

[HoytRen]

I see only 1 implementation. Tell me if here are more.

Close #998

[codecov-commenter]

Codecov Report

Merging #1213 (37b1d8b) into main (18860df) will increase coverage by 0.16%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #1213      +/-   ##
==========================================
+ Coverage   55.76%   55.92%   +0.16%     
==========================================
  Files         161      161              
  Lines        9650     9645       -5     
==========================================
+ Hits         5381     5394      +13     
+ Misses       3740     3720      -20     
- Partials      529      531       +2     

Impacted Files	Coverage Δ
service/rpc/state.go	0.00% <ø> (ø)
state/core_access.go	12.34% <0.00%> (-0.85%)	:arrow_down:
header/core/listener.go	52.83% <0.00%> (-5.67%)	:arrow_down:
ipld/get_namespaced_shares.go	88.32% <0.00%> (-2.19%)	:arrow_down:
fraud/pb/proof.pb.go	36.61% <0.00%> (+1.89%)	:arrow_up:
share/discovery.go	35.41% <0.00%> (+3.12%)	:arrow_up:

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[HoytRen]

Rebased twice, and it still failed...

[Wondertan]

Yeah, we have some flakiness in tests

[HoytRen]

happy to see it passed :)