Validate breakpoint resolution in sourcemapped scripts

[connor4312]

Previous versions of the debug adapter had breakOnLoad options that we used to ensure scripts and breakpoints were set before evaluating the script. PWA works a little more intelligently by using the beforeScriptWithSourceMapExecution instrumentation breakpoint and resolving and user-defined breakpoints at that time. This seems to work well in my testing, but we should monitor and ensure that there aren't edge cases it ends up missing.

bc19ac0

[connor4312]

We ran into issues here when debugging VS Code extensions. The existing sourcemap resolution logic behaves quite well if the debugee contains mostly or only our own code, but is tripped up when there's third-party sources that conflict with the ones we're interested in.

[connor4312]

Moving this out to other more specific issues