Cleanup remaining usage of NonNull and Nullable

[netopyr]

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👾 Description of the issue

There are various libraries that offer @NonNull and @Nullable annotations. In the past, different teams used different libraries, which led to confusion. Meanwhile, we have standardized the usage and only use the annotations from the package edu.umd.cs.findbugs.annotations. However, there are still a few classes in which other annotations are used.

At least these two classes still use the wrong annotation:

• com.hedera.node.app.service.contract.impl.ContractServiceComponent
• com.hedera.services.bdd.junit.hedera.embedded.fakes.FakePlatformContext

Steps to reproduce

See in the import. All @NonNull and @Nullable imports should use the package edu.umd.cs.findbugs.annotations. The @NotNull annotation should not be used anymore.

Proposed Solution:

Search for all places where the wrong annotation is used and replace it with the correct one from edu.umd.cs.findbugs.annotations.

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[Ayush-Baranwal]

hi @netopyr I would like to contribute to this issue.

[netopyr]

Hi @Ayush-Baranwal! Welcome, and please go ahead! If you have any questions, do not hesitate to ask.