retrieval: Only output matching nodes, MatchPath dagspec

[magik6k]

Depends on ipld/go-ipld-selector-text-lite#5

todo:

• Use go-ipld-selector-text-lite master when merged
• Test non-path-matching retrieval
• Make sure that ls / cat still works

[jennijuju]

also need ipld/go-ipld-selector-text-lite#5

[codecov]

Codecov Report

Merging #7706 (468b90a) into master (77d75b7) will decrease coverage by 0.00%.
The diff coverage is 59.45%.

@@            Coverage Diff             @@
##           master    #7706      +/-   ##
==========================================
- Coverage   39.54%   39.53%   -0.01%     
==========================================
  Files         638      638              
  Lines       68045    68069      +24     
==========================================
+ Hits        26905    26911       +6     
- Misses      36509    36536      +27     
+ Partials     4631     4622       -9     

Impacted Files	Coverage Δ
api/types.go	52.77% <ø> (ø)
cli/client_retr.go	21.29% <0.00%> (-0.24%)	⬇️
node/impl/client/client.go	50.53% <65.62%> (+0.84%)	⬆️
api/v0api/v1_wrapper.go	14.20% <100.00%> (+0.49%)	⬆️
chain/events/message_cache.go	87.50% <0.00%> (-12.50%)	⬇️
chain/stmgr/call.go	67.87% <0.00%> (-7.28%)	⬇️
chain/events/observer.go	71.64% <0.00%> (-6.72%)	⬇️
extern/sector-storage/manager_calltracker.go	57.70% <0.00%> (-4.85%)	⬇️
chain/events/events_called.go	83.90% <0.00%> (-1.96%)	⬇️
extern/storage-sealing/fsm.go	55.77% <0.00%> (-1.60%)	⬇️
... and 17 more

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[ribasushi]

Great stuff!

2 more suggestions, no functional changes