cli: Add support for dumping deployed WASM of contracts

[matevz]

• Adds contracts.CodeStorage to runtime API which returns the stored Wasm code.
• Updates client-sdk/go bindings.
• Updates client-sdk/ts-web bindings
• Implements it in oasis CLI (oasis contracts dump-code).

[codecov]

Codecov Report

Merging #1007 (a238c92) into main (d12b712) will decrease coverage by 0.02%.
The diff coverage is 52.94%.

@@            Coverage Diff             @@
##             main    #1007      +/-   ##
==========================================
- Coverage   67.99%   67.96%   -0.03%     
==========================================
  Files         128      128              
  Lines       11001    11017      +16     
==========================================
+ Hits         7480     7488       +8     
- Misses       3489     3497       +8     
  Partials       32       32              

Impacted Files	Coverage Δ
client-sdk/go/modules/contracts/contracts.go	0.00% <0.00%> (ø)
client-sdk/go/modules/contracts/types.go	40.00% <ø> (ø)
runtime-sdk/modules/contracts/src/code.rs	100.00% <ø> (ø)
runtime-sdk/modules/contracts/src/types.rs	95.23% <ø> (ø)
runtime-sdk/modules/contracts/src/lib.rs	65.02% <83.33%> (+0.31%)	⬆️
runtime-sdk/modules/contracts/src/test.rs	97.60% <100.00%> (+0.03%)	⬆️

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