Use Display impl instead of ToString

[dani-garcia]

Type of change

- [ ] Bug fix
- [ ] New feature development
- [x] Tech debt (refactoring, code cleanup, dependency upgrades, etc)
- [ ] Build/deploy pipeline (DevOps)
- [ ] Other

Objective

Latest Rust 1.78 includes a clippy warning when implementing ToString directly instead of using Display, which would also derive ToString for free. Note that there are a few uses of impl ToString in the bitwarden-api-* packages but I haven't changed those here. I've opened a PR in openapi-generator OpenAPITools/openapi-generator#18633

[github-actions]

Checkmarx One – Scan Summary & Details – edbb70b8-448b-4dc9-8422-116a9fff74a5

New Issues

Severity	Issue	Source File / Package	Checkmarx Insight
	Unpinned Actions Full Length Commit SHA	/version-bump.yml: 52	Pinning an action to a full length commit SHA is currently the only way to use an action as an immutable release. Pinning to a particular SHA helps...

Fixed Issues

Severity	Issue	Source File / Package
	Unpinned Actions Full Length Commit SHA	/release-cpp.yml: 61
	Unpinned Actions Full Length Commit SHA	/release-cpp.yml: 67
	Unpinned Actions Full Length Commit SHA	/version-bump.yml: 53

[codecov]

Codecov Report

Attention: Patch coverage is 40.00000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 58.69%. Comparing base (2f52f5e) to head (c88e7c8).
Report is 1 commits behind head on main.

Files	Patch %	Lines
crates/bitwarden-exporters/src/lib.rs	40.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #771   +/-   ##
=======================================
  Coverage   58.69%   58.69%           
=======================================
  Files         177      177           
  Lines       11501    11501           
=======================================
  Hits         6751     6751           
  Misses       4750     4750           

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