Red Knot - Add symbol flags

[plredmond]

First commit adds symbol flags using the bitflags package. The flags for is-defined and is-used (in the current scope) are implemented.

Second commit is a bare-sketch of the data for the 1st and 2nd passes to determine if a symbol is free/cell/implicit-global/explicit-global.

[github-actions[bot]]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[plredmond]

It says three flags are supported, but it seems like just two?

That was a typo of "these". Sorry.

I've added a commit for the other variant of Kind.