pool: update the runahead limit after task removal

[oliver-sanders]

• Update the runahead limit when tasks are removed (i.e. by suicide trigger) to prevent erroneous stall.
• Also closes data store: blocked tasks outside of n=1 are missing from the store #4983 (by adding a test for it)

Whilst writing the test, I noticed the n-window values for the "bar" tasks look wrong to me, although that's a different issue.

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Applied any dependency changes to both setup.cfg (and conda-environment.yml if present).
• Tests are included (or explain why tests are not needed).
• Changelog entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[hjoliver]

Suggested change

	Ensure the runahead limit is recomputed when legacy "suicide-triggers" are used to prevent erroneous stall in niche cases.
	Ensure the runahead limit is recomputed when legacy "suicide-triggers" are used, to prevent erroneous stall in niche cases.

(A bit ambiguous without the comma)

[hjoliver]

Whilst writing the test, I noticed the n-window values for the "bar" tasks look wrong to me, although that's a different issue.

Needs an issue?

[oliver-sanders]

Needs an issue?

I think so, just checking that it's wrong before doing so.