feat(testing): Unify VSCode debug config

[lobsterkatie]

For a long time, we've had the following TODO in our VSCode launch.json (debug config) file:

// TODO: these are all alike save the package, so figure out how to make that variable

which was there because we had an ever-expanding number of nearly identical configurations, one per package. Each time we wanted to debug the tests in a new package, we had to copy and paste and make a new PR to get it on master. It was inefficient and frankly kind of a pain.

When the need for yet another package's tests to be debugged came up, rather than continue the madness, I finally answered that TODO. This PR does a few things to make that happen:

• Add an inputs section to the debug configuration, to allow more than the standard values in the config to be dynamic. - Include a command for reading the one part of the config that has been different per config entry - the package name - off of the open test file.
• Use that command in the now-unified debug config.
• Add the VSCode extension which enables the input command to the list of recommended extensions, and a note about it to launch.json.
• Add a "Debugging Tests" section to CONTRIBUTING.md explaining how to use the debugger.

There's also a small amount of cleanup done to both the newly-unified config entry and the one other remaining one (which runs nextjs integration tests).

[github-actions]

size-limit report

Path	Size
@sentry/browser - CDN Bundle (gzipped)	22.47 KB (-0.01% 🔽)
@sentry/browser - Webpack	23.35 KB (0%)
@sentry/react - Webpack	23.39 KB (0%)
@sentry/browser + @sentry/tracing - CDN Bundle (gzipped)	29.92 KB (-0.01% 🔽)

[AbhiPrasad]

Would really appreciate a note somewhere (maybe CONTRIBUTING.md?) on how to best use these new debug configs.

[lobsterkatie]

Would really appreciate a note somewhere (maybe CONTRIBUTING.md?) on how to best use these new debug configs.

The comments in launch.json are meant to cover that, but it's a good idea to put it in CONTRIBUTING.md also. Have added a Debugging Tests section.

[AbhiPrasad]

Sweet, thanks for adding the contributing docs.