onDeleteURI indicates a page is removed from the DB, onDeleteVisits that visits to a page have been removed. The latter can also be a partial removal or a complete one.
If onDeleteURI is sent, onDeleteVisits is not, even if all the visits are removed.

This is a lot of complication and a bit confusing, we should analyze the consumers, and try to come up with a single notification, maybe a page-removed with removedFromStore and removedAllVisits boolean properties?

Depends on D100461

Depends on D101114

Depends on D101115

Depends on D101116

Depends on D101117

Depends on D101118

Backed out for node failures

backout: https://hg.mozilla.org/integration/autoland/rev/ffed7ebd405ac9b6b0d7bf862190a63019ecb9f1

push: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&selectedTaskRun=HtxwRalQSXSuhn2Vtvw2FQ.0&revision=e714440f6c0d5eab905f2388bf89c4ca9fc47178&searchStr=linux%2C18.04%2Cx64%2Copt%2Cnode%2Ctests%2Csource-test-node-newtab-unit-tests%2Cnewtab

failure log: https://treeherder.mozilla.org/logviewer?job_id=329967416&repo=autoland&lineNumber=95

[task 2021-02-15T03:38:01.237Z] TEST START | karma
[task 2021-02-15T03:38:40.929Z] npm ERR! code ELIFECYCLE
[task 2021-02-15T03:38:40.929Z] npm ERR! errno 1
[task 2021-02-15T03:38:40.929Z] npm ERR! activity-streams@1.14.3 testmc:unit: karma start karma.mc.config.js
[task 2021-02-15T03:38:40.929Z] npm ERR! Exit status 1
[task 2021-02-15T03:38:40.929Z] npm ERR!
[task 2021-02-15T03:38:40.929Z] npm ERR! Failed at the activity-streams@1.14.3 testmc:unit script.
[task 2021-02-15T03:38:40.929Z] npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
[task 2021-02-15T03:38:40.929Z]
[task 2021-02-15T03:38:40.929Z] npm ERR! A complete log of this run can be found in:
[task 2021-02-15T03:38:40.929Z] npm ERR! /builds/worker/.npm/_logs/2021-02-15T03_38_40_886Z-debug.log
[task 2021-02-15T03:38:40.945Z] TEST-UNEXPECTED-FAIL karma | activity-stream:PlacesFeed:Custom dispatch should only dispatch 1 PLACES_LINKS_CHANGED action if any page-removed notifications happened at once: expected spy to be called once but was called 0 times
[task 2021-02-15T03:38:40.945Z] fail@http://localhost:9876/base/node_modules/sinon/pkg/sinon.js?fd64f3a13cddbb3783308d595307f8f6c1c10a4b:167:21
[task 2021-02-15T03:38:40.945Z] failAssertion@http://localhost:9876/base/node_modules/sinon/pkg/sinon.js?fd64f3a13cddbb3783308d595307f8f6c1c10a4b:126:16
[task 2021-02-15T03:38:40.945Z] mirrorPropAsAssertion/assert[name]@http://localhost:9876/base/node_modules/sinon/pkg/sinon.js?fd64f3a13cddbb3783308d595307f8f6c1c10a4b:152:26
[task 2021-02-15T03:38:40.945Z] @http://localhost:9876/base/test/unit/unit-entry.js?f81030d388b3cf5ce8bdeb6c829b185d7f001dad:154291:14
[task 2021-02-15T03:38:40.945Z]
[task 2021-02-15T03:38:40.945Z] TEST-UNEXPECTED-FAIL karma | activity-stream:PlacesFeed:PlacesObserver:#page-removed should dispatch a PLACES_LINK_DELETED action with the right url: expected spy to be called with arguments
[task 2021-02-15T03:38:40.945Z] fail@http://localhost:9876/base/node_modules/sinon/pkg/sinon.js?fd64f3a13cddbb3783308d595307f8f6c1c10a4b:167:21
[task 2021-02-15T03:38:40.945Z] failAssertion@http://localhost:9876/base/node_modules/sinon/pkg/sinon.js?fd64f3a13cddbb3783308d595307f8f6c1c10a4b:126:16
[task 2021-02-15T03:38:40.945Z] mirrorPropAsAssertion/assert[name]@http://localhost:9876/base/node_modules/sinon/pkg/sinon.js?fd64f3a13cddbb3783308d595307f8f6c1c10a4b:152:26
[task 2021-02-15T03:38:40.945Z] @http://localhost:9876/base/test/unit/unit-entry.js?f81030d388b3cf5ce8bdeb6c829b185d7f001dad:154319:16
[task 2021-02-15T03:38:40.945Z]
[task 2021-02-15T03:38:40.946Z] { checkBundles: true, karma: false }
[task 2021-02-15T03:38:40.947Z] CODE 1
[taskcluster 2021-02-15 03:38:41.248Z] === Task Finished ===
[taskcluster 2021-02-15 03:38:41.248Z] Unsuccessful task run with exit code: 1 completed in 72.762 seconds

https://hg.mozilla.org/mozilla-central/rev/3ba9536a50cb
https://hg.mozilla.org/mozilla-central/rev/d834ae135986
https://hg.mozilla.org/mozilla-central/rev/3e51a8ea19c3
https://hg.mozilla.org/mozilla-central/rev/6b16c2d4f144