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ARROW-16424: [C++] Use Uri to parse substrait ReadRel file path (#14071)

A PR to subsume #13390

I tried to add on to #13390, but then I rebased and now it seems really complicated to add to that PR.

This PR primarily uses `Uri` to parse file URIs extracted from `substrait::ReadRel`. This occurs when `FromProto` is called on a `Relation` that is a read type (`ReadRel`). Additionally, to make `FromProto` a bit more readable, I moved the code for this case into a separate function, `FromReadRelation`. This function has the following overall flow:

1. Validate ReadRel
2. Initialize FileFormat from the 1st file URI
3. foreach file URI:
    1. Validate the proto URI
    2. Parse using the Uri class
    3. Validate the Uri (should be a `file:///` path)
    4. Accumulate `FileInfo` instances using `LocalFileSystem`
4. return DeclarationInfo for dataset scan over the file URIs


Validation functions are prefixed with `Check` to match `CheckRelCommon`.

Lead-authored-by: Aldrin M <octalene.dev@pm.me>
Co-authored-by: Aldrin Montana <octalene.dev@pm.me>
Co-authored-by: octalene <octalene.dev@pm.me>
Signed-off-by: Antoine Pitrou <antoine@python.org>