NavigatorScreen: satisfy exhaustive-deps eslint rule

[flootr]

What?

Ensure NavigatorScreen satisfy the exhaustive-deps eslint rule

Why?

Part of the effort in #41166 to apply the exhaustive-deps eslint rule to the components package

How?

In the useEffect call we're manipulating the location object (stored in context) by setting hasRestoredFocus to a boolean value. Due to that assignment the exlint rule expects the whole location object to be a dependency of the useEffect call which isn't what we want. Therefore we use a workaround by storing the location object in ref locationRef and access/write to it that way.

Testing Instructions

1. From your local Gutenberg directory, run npx eslint --rule 'react-hooks/exhaustive-deps: warn' packages/components/src/navigatior/navigator-screen
2. Confirm that the linter returns no errors or warnings
3. Confirm navigator unit tests still pass
4. Run Storybook locally, confirm the Navigator component stories and/or docs still work as expected

Screenshots or screencast

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[ciampo]

Changes LGTM 🚀

I tested in particular for the regression fixed in #44972, everything worked as expected.

Could you please add a CHANGELOG entry ?