Migrate ollama to jackson

[Martin7-1]

Issue

#1042

Change

Migrate Ollama module from Gson to Jackson. But we still need to migrate langchain4j-core and openai4j too.

Note that there are three things confused me(these issues exist in original ollama module):

1. I observe that some tests with inputTokenCount Assertion (such as assertThat(tokenUsage.inputTokenCount()).isEqualTo(35)) failed because of the differencet count of input tokens. I don't know whether it's because Ollama's update. Now I correct it
2. should_propagate_failure_to_handler_onError in Streaming{xxx}ModelIT failed in my local because NullPointerException do not have any message. Is it a problem in my local environment?
3. Somtimes if I run tests individually, all tests will pass. But if I run them in the same time(such as using command line rather than IDE), they will failed due to some strange reasons(e.g. input token usage will be null). I think Maybe it's a network problem or Testcontainers's problem.

I'm not sure if these problems are due to my local environment, so if you have any suggestions or solutions, please let me know!

General checklist

• There are no breaking changes
• I have added unit and integration tests for my change
• I have manually run all the unit and integration tests in the module I have added/changed, and they are all green
• I have manually run all the unit and integration tests in the core and main modules, and they are all green

• I have added/updated the documentation
• I have added an example in the examples repo (only for "big" features)

Checklist for adding new model integration

• I have added my new module in the BOM

Checklist for adding new embedding store integration

• I have added a {NameOfIntegration}EmbeddingStoreIT that extends from either EmbeddingStoreIT or EmbeddingStoreWithFilteringIT
• I have added my new module in the BOM

Checklist for changing existing embedding store integration

• I have manually verified that the {NameOfIntegration}EmbeddingStore works correctly with the data persisted using the latest released version of LangChain4j

[langchain4j]

Hi @Martin7-1 thanks a lot! I will try to review it asap!

[langchain4j]

Hi, thanks a lot!
This PR should wait till we release the first migration from Gson to Jackson (Anthropic module) and see that it actually works.
We can then proceed with this PR and migrating other modules.