Handle chunks containing multiple EOL (#6146)

[dgaspar]

Folks trying to use VueJS were having trouble relying on ScriptRunner, as it didn't detect (via string matching) the completion of a vue-cli build when in debug mode.
The issue was discussed here: EEParker/aspnetcore-vueclimiddleware#2 (comment)
The fix in this PR ( credit to @EEParker EEParker/aspnetcore-vueclimiddleware@a169dd6#diff-6d394759c0a824a137b47986d0cce571R158 ) ensured that a OnCompleteLine() was called for every single received line (and not just the first line of the chunk).

Addresses #6146

[dnfclas]

All CLA requirements met.

[SteveSandersonMS]

@ryanbrandenburg Do you consider yourself to have ownership of this area, and would you like to review this PR?

[mkArtakMSFT]

@ryanbrandenburg waiting for your review on this one.

[ryanbrandenburg]

This code seems fine as far as I can tell, but it makes me nervous that we don't have any tests for this area. Could I get you to add a test project for SpaServices.Extensions in this PR as well? It doesn't have to be complicated, just one test for the scenario of this PR would be fine. There's an example of unit tests for middleware here. No biggy if not, I can file an issue to come back and do it later, but it might be a while.

[mkArtakMSFT]

@ryanbrandenburg let's get this merged and also add a new work item for us to add test coverage for this area, if we don't currently have any.