Allow configuration of max number of parallel Tentacle upgrades

[N-lson]

Prerequisites

• [ ] I have searched open and closed issues to make sure it isn't already requested
• [ ] I have discussed this in #feature-discussion or #backlog and the consensus is that this is something we plan on adding in the near future
• [ ] I have written a descriptive issue title
• [ ] I have linked the original source of this feature request
• [ ] I have labelled the value stream (area/core, area/steps, ...)
• [ ] I have added the kind/enhancement label

The enhancement

What is the problem this solves or benefit it gives

Tentacle upgrades have a fixed limit based on the number of processors. This doesn't make much sense since Tentacle upgrades aren't a CPU intensive task. This option should be made configurable so that customers that have many Tentacles are able to upgrade them much more efficiently.

Proposed solution

Add a new configuration setting in Octopus which defines how many Tentacles can be upgraded at a time.

[Octobob]

:tada: The fix for this issue has been released in:

Release stream	Release
2022.3	2022.3.9953
2022.4+	all releases

[N-lson]

See https://github.com/OctopusDeploy/Issues/issues/8059