Make it possible to post a single comment for all plans

[motatoes]

In case of larger monorepos of 10+ projects, a single digger plan command could be generating over 10 commands leading to too much noise. We should allow users to configure posting only a single comment for digger plan/digger apply commands.

paramenter: post-single-comment (default false)

if true then digger will only publish a single comment with all the plans aggregated for this comment (also collapsed by default as with single comments)

[ZIJ]

Adding the underlying problem flagged by @fleroux514:

"One feedback from the team is that is generates a lot of PR comments."

[ZIJ]

@fleroux514: "Wondering if we it could even go one step further and also regroup comments about locks being acquired / released, multiple applyoutputs, and failing apply comment.. Think it would be even cleaner and consistent."