feat: Bump MSRV to 1.86.0

[scouten-adobe]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.54%. Comparing base (9ce019f) to head (1457f56).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1269   +/-   ##
=======================================
  Coverage   79.54%   79.54%           
=======================================
  Files         151      151           
  Lines       42722    42722           
=======================================
+ Hits        33982    33983    +1     
+ Misses       8740     8739    -1     

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[gpeacock]

We can't use the new feature until this pinned test is updated:

• name: Install Rust toolchain
  uses: dtolnay/rust-toolchain@master
  with:
  toolchain: nightly-2025-01-24
  # Pinning to specific nightly build for now. More recent versions
  # (not sure of start date) cause linker problems with OpenSSL native
  # code on Mac and Windows, but only when built with minimal dependencies.
  # Problem discovered on 2025-01-27.
  # TO DO: Investigate and file bugs if necessary against rust-lang.

[gpeacock]

We need to update this pinned test in ci.yml. It ties us to an older rust version.

https://github.com/contentauth/c2pa-rs/actions/runs/16588277907/job/46917859474?pr=1266

• name: Install Rust toolchain
  uses: dtolnay/rust-toolchain@master
  with:
  toolchain: nightly-2025-01-24
  # Pinning to specific nightly build for now. More recent versions
  # (not sure of start date) cause linker problems with OpenSSL native
  # code on Mac and Windows, but only when built with minimal dependencies.
  # Problem discovered on 2025-01-27.
  # TO DO: Investigate and file bugs if necessary against rust-lang.

[scouten-adobe]

@gpeacock that test was updated in #1270. Please re-review.