feat: backport more improvements for Next 9 users

[ehmicky]

This PR backports more improvements available in the latest version of this plugin, but not available to Next 9 users to them being stuck on the v1 on this plugin:

• Use netlify/functions instead of netlify-automatic-functions (Use new default functions directory #87)
• Remove next as a peer dependency (remove next as peer dependency #96)
• Decrease npm package size (chore: decrease package size #101)

Important: This PR should be merged to the v1 git branch, not main. It should then be released as 1.*.*, not 3.*.*. npm publish --tag=deprecated should be used.

Also cc @erezrokah would did other backports on that branch.

[lindsaylevine]

ty <3