docs: add better organization of third-party docs

[moldy530]

Pull Request Checklist

• Did you add new tests and confirm existing tests pass? (yarn test)
• Did you update relevant docs? (docs are found in the site folder, and guidelines for updating/adding docs can be found in the contribution guide)
• Do your commits follow the Conventional Commits standard?
• Does your PR title also follow the Conventional Commits standard?
• If you have a breaking change, is it correctly reflected in your commit message? (e.g. feat!: breaking change)
• Did you run lint (yarn lint:check) and fix any issues? (yarn lint:write)
• Did you follow the contribution guidelines?

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PR-Codex overview

This PR focuses on restructuring sidebar links and updating references to third-party components.

Detailed summary

• Added thirdPartySidebar with links to different third-party components
• Updated links to third-party components in various MDX files
• Deprecated @alchemy/aa-signers package and updated references
• Added a new autogenerated file generatePrivateKeySigner with usage information

The following files were skipped due to too many changes: aa-sdk/core/src/signer/local-account.ts, site/sidebar/shared.ts, site/pages/third-party/chains.mdx, site/pages/smart-contracts/custom/using-your-own.mdx, site/pages/signer/custom-signer.mdx, site/pages/third-party/paymasters.mdx

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Name	Status	Preview	Comments	Updated (UTC)
aa-sdk-site	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 6, 2024 7:06pm
aa-sdk-ui-demo	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 6, 2024 7:06pm