refactor(torii): don't use feature-only type in non-feature code

[kariy]

Create a new SchemaError type to be used in the schema module, and replace the usage of ClientError because it is feature-gated.

Previously running cargo check -p torii would result in error where the ClientError is not found because torii crate doesn't rely on the client feature which the error type is hidden under.

[codecov]

Codecov Report

Attention: Patch coverage is 46.15385% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 70.31%. Comparing base (a3587b3) to head (7022ea0).

Files	Patch %	Lines
crates/torii/grpc/src/types/schema.rs	60.00%	4 Missing ⚠️
crates/torii/grpc/src/client.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1894      +/-   ##
==========================================
- Coverage   70.31%   70.31%   -0.01%     
==========================================
  Files         315      315              
  Lines       35841    35843       +2     
==========================================
  Hits        25203    25203              
- Misses      10638    10640       +2     

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[glihm]

Thanks for this fix mate.