Use GetSync in Request Validation

[hannahhoward]

Goals

Fix a race condition where deal status in request validation could fall behind actual events dispatched (resulting in state = StorageDealAcceptWait when Get was called, which then caused a deal rejection)

Implementation

• Move registering of voucher types for storage market into storage market constructor (long holdover of original way markets was extracted from lotus)
• Use an interface to abstract how deals are "gotten" from the store in Request Validator
• Provide implementation of said interface for client and provider (still assumes multi-process model with seperate data transfer -- we'll need to think about what we want to do if this ever goes back in go-filecoin)
• Register storage voucher types in constructors for client and provider
• Move all of these little "environment wrappers" -- implementations of bridge interfaces between the client/provider and various utility modules -- into seperate environments file -- mirroring retrieval

[codecov-commenter]

Codecov Report

Merging #372 into master will decrease coverage by 0.32%.
The diff coverage is 3.07%.

@@            Coverage Diff             @@
##           master     #372      +/-   ##
==========================================
- Coverage   61.78%   61.47%   -0.31%     
==========================================
  Files          41       43       +2     
  Lines        2857     2870      +13     
==========================================
- Hits         1765     1764       -1     
- Misses        941      955      +14     
  Partials      151      151              

Impacted Files	Coverage Δ
storagemarket/impl/client.go	2.95% <0.00%> (+0.23%)	⬆️
storagemarket/impl/client_environments.go	0.00% <0.00%> (ø)
storagemarket/impl/provider.go	3.02% <0.00%> (+0.49%)	⬆️
storagemarket/impl/provider_environments.go	0.00% <0.00%> (ø)
...mpl/requestvalidation/unified_request_validator.go	75.00% <33.34%> (ø)
storagemarket/impl/requestvalidation/common.go	87.10% <100.00%> (-0.40%)	⬇️

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[ingar]

Looks good to me. I still get confused by push/pull...