Switch to node 18, node 16 no longer works with Firebase CLI.

[jonsimantov]

Description

Provide details of the change, and generalize the change in the PR title above.

Firebase CLI (and Firestore emulator) now require Node 18 minimum, so install that on our runners instead of 16.

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Testing

Describe how you've tested these changes. Link any manually triggered Integration tests or CPP binary SDK Packaging Github Action workflows, if applicable.

Tests in this PR, this should also fix the Firestore desktop nightlies.

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Type of Change

Place an x the applicable box:

• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

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Notes

• Bug fixes and feature changes require an update to the Release Notes section of release_build_files/readme.md.
• Read the contribution guidelines CONTRIBUTING.md.
• Changes to the public API require an internal API review. If you'd like to help us make Firebase APIs better, please propose your change in a feature request so that we can discuss it together.

[github-actions]

❌  Integration test FAILED

Requested by @jonsimantov on commit cd5c493
Last updated: Tue Dec 12 16:45 PST 2023
View integration test log & download artifacts

Failures	Configs
auth	[TEST] [FLAKINESS] [Android] [2/3 os: ubuntu windows] [1/2 android_device: android_target] (1 failed tests)   CRASH/TIMEOUT
firestore	[TEST] [ERROR] [Android] [1/3 os: macos] [1/2 android_device: android_target] [TEST] [FLAKINESS] [iOS] [macos] [1/2 ios_device: ios_target] (6 failed tests)   ServerTimestampTest.TestServerTimestampsCanReturnEstimatedValue   ServerTimestampTest.TestServerTimestampsCanReturnPreviousValue   ServerTimestampTest.TestServerTimestampsWorkViaSet   ServerTimestampTest.TestServerTimestampsWorkViaTransactionSet   ServerTimestampTest.TestServerTimestampsWorkViaTransactionUpdate   ServerTimestampTest.TestServerTimestampsWorkViaUpdate
gma	[TEST] [ERROR] [iOS] [macos] [All 2 ios_device] [TEST] [FLAKINESS] [Android] [2/3 os: ubuntu macos] [1/2 android_device: android_target] (1 failed tests)   CRASH/TIMEOUT
remote_config	[TEST] [FLAKINESS] [Android] [1/3 os: macos] [1/2 android_device: android_target] (1 failed tests)   CRASH/TIMEOUT

Add flaky tests to go/fpl-cpp-flake-tracker