[env] Wrap all RPC calls in reset() in retry loop.

[ChrisCummins]

This adds a new Docker image that contains a preconfigured CompilerGym install that can be used to run environments in an isolated container and communicated with over gRPC.

Summary of changes:

• Added a new --run_on_port=1234 flag to compiler_gym.bin.service that starts a service on the given port.
• Made the --service and --local-service-binary flags compatible with the new datasets API (Redesign of DataSet API #45).
• Made Benchmark.from_file() compatible with distributed services by reading the file contents into a protobuf, rather than embedding the local filesystem path (Redesign of DataSet API #45).
• Fixed an unrelated type error bug when switching reward space midway through an episode.

[codecov-commenter]

Codecov Report

Merging #423 (653f65d) into development (03f0a3b) will increase coverage by 0.00%.
The diff coverage is 50.00%.

@@             Coverage Diff              @@
##           development     #423   +/-   ##
============================================
  Coverage        87.29%   87.30%           
============================================
  Files              100      100           
  Lines             5746     5749    +3     
============================================
+ Hits              5016     5019    +3     
  Misses             730      730           

Impacted Files	Coverage Δ
compiler_gym/envs/compiler_env.py	88.91% <50.00%> (+0.33%)	⬆️
compiler_gym/envs/llvm/datasets/cbench.py	78.37% <0.00%> (-0.78%)	⬇️
compiler_gym/envs/gcc/service/gcc_service.py	97.75% <0.00%> (+0.37%)	⬆️

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