Rework breakpoints api

[pokey]

As of #1143, the ide api supports breakpoints. We'd like to revisit this new breakpoints api, with an eye to making it non-VSCode-specific, while also trying to remove Cursorless logic from the VSCode implementation. In particular, we'd like to answer the following questions:

• Should the logic that determines which breakpoints to add and which to remove be part of the VSCode implementation, or part of the ToggleBreakpoint action?
• What does the breakpoint api look like for other editors?
• Should we be setting line breakpoints to position 0 in the ToggleBreakpoint action, or in the VSCode implementation?
• How do we distinguish between line and inline breakpoints?

We may want to partially revert to the old implementation https://github.com/cursorless-dev/cursorless/blob/cfdc29b54a8744aec141358adbe28c9ea7dd157f/src/actions/ToggleBreakpoint.ts

[pokey]

Let's close this, and revisit if contributors run into issues implementing breakpoints for other IDEs