docs: deprecate clipboard API access from renderer processes

[jkleinsc]

Description of Change

As documented in the Clipboard Module Rearchitecture RFC, direct access to the clipboard API from the renderer will be removed. This PR adds a deprecation message in preparation for the changes coming as part of the Clipboard Module Rearchitecture.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant API documentation, tutorials, and examples are updated and follow the documentation style guide
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Deprecated clipboard API access from renderer processes

[electron-cation]

🪦 Deprecation Checklist

🔥 New deprecations in this PR

• 📢 Are called out in docs/breaking-changes.md
• ⚠️ Use the deprecation helpers in lib/common/deprecate.ts to warn about usage (including events)
• 📝 Are marked as deprecated in the docs, using _Deprecated_ (including properties and events)
• 🧪 Relevant tests are updated to expect deprecation messages using the helpers in spec/lib/warning-helpers.ts

---

@electron/wg-releases: Please confirm these deprecation changes conform to our deprecation policies listed in docs/breaking-changes.md, then check the applicable items in the checklist and remove any non-applicable items.

[dsanders11]

It looks like we don't have any direct tests of using the clipboard API in the renderer, so I'm OK with skipping the final item in the deprecation review checklist regarding confirming deprecation messages in tests.

Note to future us, we'll need to update the paste execCommand test in spec/chromium-spec.ts since it makes use of the clipboard API from the renderer for those tests.

[release-clerk]

Release Notes Persisted

Deprecated clipboard API access from renderer processes

[trop]

I have automatically backported this PR to "40-x-y", please check out #48923