out_mongo: add MongoDB as default output plugin

[w4term3loon]

MongoDB output plugin as a default plugin to ease the process of setting up the connection between such databases and Fluent-bit.

I've opended an issue for the missing feature:

https://github.com/fluent/fluent-bit/issues/8846

• [x] Add MongoDB prerequisites to cmake build.
• [ ] Implement output plugin.
• [ ] Add cmake config options if needed.
• [ ] Add mongo-c-driver project to lib (may be unnecessary).
• [ ] Format code to match guidelines.

Addresses #8846

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Testing Before we can approve your change; please submit the following in a comment:

• [ ] Example configuration file for the change
• [ ] Debug log output from testing the change

• [ ] Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to the packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• [N/A] Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• [ ] Documentation required for this feature

Backporting

• [ ] Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.