Add throttle groups (sequential execution) within phases

[blt04]

Throttle groups allow you to execute specific jobs within a phase in serial. For example, if you have jobs A, B, and C, the default behavior executes them in parallel, for example:

A....
B......
C...

If we assign the same "throttle group" (a string) to jobs A and C, they will execute in series (C will not start until A finishes). This would look like:

A....
B......
     C...

Throttle groups add another level of customization to MultiJobs. They support variable expansion and treat the "false" string as no throttle group - so they can be easily attached to boolean build parameters.

[jenkinsadmin]

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[calebmayeux]

Really excited about this new feature, as it'll add a powerful and much needed functionality to multijobs.

I foolishly only checked open Jira tickets and didn't check pull requests before starting to implement this, and ended up implementing scarily similar code almost 3 weeks after you submitted this pull request. Haven't tested your changes, but reviewing the code it looks good.

Thanks! Hope they merge this in for the next release.

[harcher81]

I like, but why this is not already merge?

I will fix some deadlocks and the merge will be difficult.

[misery]

Any progress here?

[rhass-r7]

This may need to be rebased/merged with the current head of master.

[hagzag]

IMO, This is a bit against the Multijob logic, if you want jobs to be built in parallel you should move them to a separate phase ...

[hagzag]

@itaior @cohencil I think this PR is long gone code wise + it's against our logic no ?

[itaior]

I think PR #92 achieve the same behavior , So it's needed. let compare and decide

[hagzag]

sorry @blt04 this was implemented in PR 92.