Update Rust version to 1.65.0

[soareschen]

Closes: #2818

Description

Update the minimum version bound of Rust to 1.65. This will allow us to make use of new language features in Rust, most notably Generic Associated Types.

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PR author checklist:

• Added changelog entry, using unclog.
• Added tests: integration (for Hermes) or unit/mock tests (for modules).
• Linked to GitHub issue.
• Updated code comments and documentation (e.g., docs/).
• Tagged one reviewer who will be the one responsible for shepherding this PR.

Reviewer checklist:

• Reviewed Files changed in the GitHub PR explorer.
• Manually tested (in case integration/unit/mock tests are absent).

[mzabaluev]

Please also update the MSRV in README.md.
The full checklist is in an issue template, which itself needs to be updated because some items no longer apply.

[soareschen]

Please also update the MSRV in README.md. The full checklist is in an issue template, which itself needs to be updated because some items no longer apply.

Done.