Update react monorepo to v19 (major) (#28914)

* Update react monorepo to v19

* Import JSX explicitly for React 19 compatibility

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Update usages of refs for React 19 compatibility

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Update react imports

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* Avoid legacy contexts as much as possible

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* Avoid deprecated React symbols

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* Stash

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* Update usages of refs for React 19 compatibility

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Iterate

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* Switch pillify to use a html-react-parser approach rather than DOM muddling

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* Iterate

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* Iterate react html parsing

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* Iterate react html parsing

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* Iterate html parsing

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* Memoize the EventContentBody component

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* Iterate html parsing

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* Iterate

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* Iterate

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* Simplify

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* Iterate

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* Discard changes to src/Linkify.tsx

* Discard changes to src/components/views/messages/TextualBody.tsx

* Discard changes to src/settings/handlers/AbstractLocalStorageSettingsHandler.ts

* Iterate

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* Iterate

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* Iterate

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* Iterate

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* Iterate

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* Prepare for React 19 upgrade

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* Iterate

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* Remove stale comment

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---------

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Michael Telatynski <7t3chguy@gmail.com>

test/unit-tests/components/views/polls/pollHistory/__snapshots__/PollHistory-test.tsx.snap

@@ -91,7 +91,7 @@ exports[`<PollHistory /> renders a list of active polls when there are polls in
             tabindex="0"
           >
             <div
-              aria-labelledby=":rc:"
+              aria-labelledby=":ra:"
               class="mx_PollListItem_content"
             >
               <span>
@@ -116,7 +116,7 @@ exports[`<PollHistory /> renders a list of active polls when there are polls in
             tabindex="0"
           >
             <div
-              aria-labelledby=":rh:"
+              aria-labelledby=":rf:"
               class="mx_PollListItem_content"
             >
               <span>