Add Debug_FailFast configuration

[krschau]

Summary of the pull request

Turning FailFastOnErrors back on again (#3244) exposed a new crash, and we expect more as we iron things out. Instead of continuing to turn it off and on, this change creates a new Debug configuration called Debug_FailFast, which developers can choose to use when it works for them.

Most changes done by Visual Studio, except defining and using the DEBUG_FAILFAST constant.

References and relevant issues

#3019

Validation steps performed

Validated locally that Debug and Debug_FailFast both had the failfast settings we expect.

PR checklist

• Closes #xxx
• Tests added/passed
• Documentation updated
• Telemetry compliance tasks completed for added/updated events

[jsidewhite]

Instead of having a configuration, can you just unconditionally set
DebugSettings.FailFastOnErrors = true;
in each component that is currently clean? (then unset it when it's done.)

(or better - set it false in each messy component and set to true at the end of it.)

[jsidewhite]