feat: Enable event triggers in single user mode

[msfstef]

Addresses #258

In regular postgres, event triggers are disabled in single user mode as per the docs:

Event triggers are disabled in single-user mode (see postgres). If an erroneous event trigger disables the database so much that you can't even drop the trigger, restart in single-user mode and you'll be able to do that.

I've patched event_triggers.c to skip the check in order to enable them in single user mode and thus PGlite. I'm not sure what "layer" the patch belongs to @pmp-p would love your input.

I've also added a test suite for the event triggers, and did a little bit of cleanup on the build scripts since I encountered some issues while working on this.

[github-actions]

Built bundles:

• Postgres WASM: https://github.com/electric-sql/pglite/actions/runs/10562429386/artifacts/1855169419
• Interim build files: https://github.com/electric-sql/pglite/actions/runs/10562429386/artifacts/1855169534
• PGlite: https://github.com/electric-sql/pglite/actions/runs/10562429386/artifacts/1855200450
• Demos: https://github.com/electric-sql/pglite/actions/runs/10562429386/artifacts/1855215809
• Demos: https://github.com/electric-sql/pglite/actions/runs/10562429386/artifacts/1855229231

[github-actions]

🚀 Deployed on https://66cca1ada1100d2b9285e87c--pglite.netlify.app

[msfstef]

Merging this but @samwillis please do have a look when you're back from holiday to check this is the right approach as well.

[jamesgpearce]

Amazing! Let me take it for a spin.