remove old typer extra and update json -> model_dump_json (LC 0.3+ support)

[zzstoatzz]

let me know if we need some of this old pydantic syntax around for v1 backport compat or something! it was just causing me errors when installing the newest controlflow

former is causing a warning

» uv pip install -e .
Resolved 113 packages in 1.15s
   Built controlflow @ file:///Users/nate/github.com/jlowin/controlflow
Prepared 1 package in 853ms
Uninstalled 1 package in 0.66ms
Installed 1 package in 1ms
 ~ controlflow==0.9.4.dev2+ga234180 (from file:///Users/nate/github.com/jlowin/controlflow)
warning: The package `typer==0.12.5` does not have an extra named `all`

latter is causing an error (like this) on newest pydantic

TypeError: `dumps_kwargs` keyword arguments are no longer supported.

---

also fixes a couple tests and updates some to avoid warnings like pytest trying to collect TestHandler or extra marks

[jlowin]

Thanks @zzstoatzz! Combined with changing the pin (which I committed here) this should close #319. I think there's more work to do to "fully" support it but at least it's no longer breaking.