Refactor interface availability code

[bugadani]

This PR builds on top of #8 and enables bitbang-dap to set the correct capabilities based on how many pins the user provides to the constructor (in theory, unimplemented atm.).

The SWO changes allow users to:

• Omit a bunch of boilerplate if they don't need SWO support
• Correctly set the streaming trace capability. This is a best guess on my part of what this bit means, based on "support for streaming SWO trace is provided via an additional USB endpoint".
• I'm trying to come up with a way to dynamically make SWO available if there are pins available (e.g. if the probe has 4 pins, allow SWD+SWO or JTAG+no-swo). I may end up not actually doing this, but this PR takes a step in that direction.

[Copilot]

Pull Request Overview

This PR refactors the interface availability code by replacing constant flags with dynamic function calls and a bitflags‑based approach to determine capabilities.

• Refactors the Swo trait and adds a NoSwo marker struct for cases with no SWO support.
• Replaces constant AVAILABLE definitions in SWD and JTAG traits with dynamic availability functions.
• Introduces a bitflags structure in the Dap module to streamline capability reporting and update related logic.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/swo.rs	Updated Swo trait to return booleans and added the NoSwo implementation.
src/swd.rs	Replaced constant availability with a function-based check.
src/mock_device.rs	Updated SWD and JTAG implementations to use function availability.
src/jtag.rs	Replaced constant availability with a function-based check.
src/dap.rs	Introduced bitflags to represent capabilities and refactored DAP logic.