Getting workspace deps to a somewhat better state

[teh-cmc]

• Always disable default feature flags for all re_ crates when working within the workspace
• Make examples independent of workspace shenanigans and easily copy pastable

Fixes #2024 (see over there for more explanations...)

$ cd rerun_py && cargo tree -i re_viewer
re_viewer v0.6.0-alpha.0 (/home/cmc/dev/rerun-io/rerun/crates/re_viewer)
└── rerun v0.6.0-alpha.0 (/home/cmc/dev/rerun-io/rerun/crates/rerun)
    └── rerun_py v0.6.0-alpha.0 (/home/cmc/dev/rerun-io/rerun/rerun_py)

$ cargo tree --no-default-features -i re_viewer
warning: nothing to print.

PR Build Summary: https://build.rerun.io/pr/2026

[emilk]

Nice!

I think we should also add a lint to look for (and forbid) workspace in any example Cargo.toml so we don't regress here

[teh-cmc]

added workspace deps linter -- expecting clock example to fail CI in 3..2..1...

edit: yeeee