chore: bump dev version to 3.1.0-alpha.0

[ValuedMammal]

Description

This PR bumps the package version in Cargo.toml from 3.0.0 to 3.1.0-alpha.0. Also bump toolchain channel to 1.95.0 in rust-toolchain.toml.

Notes to the reviewers

Clippy fired a clippy::unnecessary_sort_by warning in tests/wallet.rs, but after looking into it the tx_amounts variable wasn't being used by the test, so instead of implementing clippy's suggestion, just remove the problematic line.

Checklists

All Submissions:

• I ran just p before pushing

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.21%. Comparing base (0217d85) to head (794a80b).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #441   +/-   ##
=======================================
  Coverage   80.21%   80.21%           
=======================================
  Files          24       24           
  Lines        5348     5348           
  Branches      242      242           
=======================================
  Hits         4290     4290           
  Misses        980      980           
  Partials       78       78           

Flag	Coverage Δ
rust	80.21% <ø> (ø)

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