[FW][ADD] MRP: Three-step manufacturing

[fw-bot]

This PR adds a new doc detailing how to manufacture products using three steps.

NOTE: There is a ref tag in this doc that does not currently work because the doc it is referencing is not yet live. The doc being referenced should be live by the time this doc is published, at which point, the ref tag will work.

Forward-Port-Of: #5163

[robodoo]

Pull request status dashboard.

[fw-bot]

@hojo-odoo cherrypicking of pull request #5163 failed.

stdout:

Auto-merging content/applications/inventory_and_mrp/manufacturing/management.rst
CONFLICT (content): Merge conflict in content/applications/inventory_and_mrp/manufacturing/management.rst

stderr:

19:34:04.803640 git.c:463               trace: built-in: git cherry-pick 7880b94e16da88ce477b4b45ad0bf0f46bd828bd
error: could not apply 7880b94e1... [ADD] MRP: Three-step manufacturing
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".
----------
status:

Either perform the forward-port manually (and push to this branch, proceeding as usual) or close this PR (maybe?).

In the former case, you may want to edit this PR message as well.

More info at https://github.com/odoo/odoo/wiki/Mergebot#forward-port

[StraubCreative]

@StraubCreative solution:

1. merge all 2-step fwps on [FW][ADD] MRP: Two-step manufacturing #6402 first
2. then cherry pick 1-step [FW][ADD] MRP: One-step manufacturing #6403 + fwp all
3. do 3-step last

[StraubCreative]

@robodoo r+