Update Rust crate snafu to 0.8

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
snafu	dependencies	minor	0.7 -> 0.8

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Release Notes

shepmaster/snafu (snafu)

v0.8.4

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Fixed

• Use the fully-qualified path to Location in the location!()
  macro.

v0.8.3

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Changed

• Report now prints an "Error: " prefix when returned directly from
  main or tests.

• Support heck version 0.5 in addition to 0.4.

v0.8.2

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Fixed

• Adding a custom Whatever variant to a generic error enum is now
  supported.

• The #[report] macro works better on functions that require more
  complicated type inference for their return types.

v0.8.1

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Added

• Error types that use constant generics are now supported.

v0.8.0

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Added

• snafu(transparent) allows creating compound error types that act
  as if they were not present, delegating thier Display and Error
  implementations to the source error. This is useful when aggregating
  smaller errors that already completely explain the failure.

• ResultExt::boxed and ResultExt::boxed_local are available to
  convert an error value into an owned trait object. This is useful
  when an error type is a generic controlled by the caller.

Changed

• Rust 1.56 is now the minimum supported Rust version. This is a
  breaking change.

• Rust 1.65 is now the default supported Rust version. This is a
  breaking change.

• The item type of the ChainCompat iterator is now &'a (dyn Error + 'b) to allow downcasting the error trait object to a concrete
  type. This is a breaking change.

• Error fields marked location are no longer automatically
  implicitly created. This is a breaking change.

• Adding #[snafu] attributes to the field of a tuple struct are now
  errors. This is a breaking change.

• The SNAFU copy of the Error trait now marks the description and
  cause methods as deprecated, following the standard library's
  example. This trait is only active when using SNAFU in a no_std
  environment and no functional difference is intended.

Removed

• The default Display implementation no longer includes the error
  text of the source error. This is a breaking change.

• The backtraces and unstable-backtraces-impl-std feature flags
  have been removed. This is a breaking change. The Backtrace
  type is now the standard library's Backtrace type when it is
  available.

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