[fix][test] Fixed nondeterministic ordering in MongoSourceTest.testWriteBadMessage

[LucasEby]

Fixes #24834

Motivation

The test was written with the incorrect assumption that the compared strings have a deterministic order. Since the original data was stored with HashMaps, which makes no guarantees to the order of it's map, the resulting strings that were compared could potentially have reordered contents. The ordering can change due to different environments producing the contents in different orders despite the logical contents being the same. Since the raw strings/trees were compared "as-is", harmless re-ordering could flip the test from pass to fail despite the data being semantically the same.

Modifications

We no longer compare the raw strings "as-is", we instead convert the strings into BsonDocuments which are ordered to fix the nondeterminism. This ensures the tests pass consistently, even in cases where the original contents were in a different order due to the usage of HashMaps.

In essence, these changes keep the spirit of the original tests while eliminating failures caused solely by allowed (but previously unexpected) reordering.

Verifying this change

• Make sure that the change passes the CI checks.

This change is already covered by existing tests, such as org.apache.pulsar.io.mongodb.MongoSourceTest#testWriteBadMessage

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository: LucasEby#4