change output buffer to setTimeout instead of setInterval

[davegarthsimpson]

Motivation

To make the buffer mechanism of the output panel more robust.

Change description

Uses a setTimeout rather that setInterval in our buffer, this ensures that flush calls do not interfere with each other. On disposing our buffer we set a boolean flag to prevent additional setTimeout callbacks from being created, if there is a setTimeout callback in progress when the buffer is "disposed" it will complete before running flush a final time to be exhaustive.

gRPC errors are also added to the buffer, to ensure proper ordering in the output panel.

Reviewer checklist

• PR addresses a single concern.
• The PR has no duplicates (please search among the Pull Requests before creating one)
• PR title and description are properly filled.
• Docs have been added / updated (for bug fixes / features)

[kittaakos]

I proposed a few changes here. What do you think?

[davegarthsimpson]

I proposed a few changes here. What do you think?

Great refactor, all LGTM

[kittaakos]

@fstasi, please review. Thank you!

[AlbyIanna]

LGTM

[davegarthsimpson]

note for traceability: changes in e5f922a were proposed/implemented by @kittaakos, then accepted and copied here by @davegarthsimpson.

[kittaakos]

The PR looks good to me. Please proceed with the merge if this is ready. Thank you!