Patch leveldb for Windows UTF16 path support

[jonsimantov]

Description

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

This change adds a patch to leveldb to enable international path support. This will only affect RTDB builds when Firestore is not included (via the cmake -DFIREBASE_INCLUDE_FIRESTORE=off flag).

The Firestore-specific fix can be found in firebase/firebase-ios-sdk#11276, and will be included in the next iOS dependency update.

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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.

The integration test was built and run against a branch of the iOS SDK with the fix, that specifically added international characters to the path. This was also manually run on a Windows machine to verify it works.

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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 with FLAKINESS (succeeded after retry)

Requested by @jonsimantov on commit c5214c0
Last updated: Fri May 12 12:20 PDT 2023
View integration test log & download artifacts

Failures	Configs
dynamic_links	[TEST] [FLAKINESS] [iOS] [macos] [1/2 ios_device: ios_target] (1 failed tests)   CRASH/TIMEOUT
firestore	[TEST] [FLAKINESS] [Android] [1/3 os: macos] [1/2 android_device: android_target] (1 failed tests)   QueryTest.TestListenUnlistenRelistenSequenceOfMirrorQueries [TEST] [FLAKINESS] [Android] [1/3 os: ubuntu] [1/2 android_device: android_target] (1 failed tests)   FirestoreIntegrationTest.TimestampsAreTruncatedToMicroseconds [TEST] [FLAKINESS] [Android] [1/3 os: windows] [1/2 android_device: emulator_ftl_target] (1 failed tests)   CRASH/TIMEOUT

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