Replace GraphQlSourceBuilderCustomizer with directly providing a SentryInstrumenter bean if missing

[adinauer]

📜 Description

We now provide a SentryInstrumenter bean directly if there is none yet instead of using GraphQlSourceBuilderCustomizer to add the instrumentation.

It is now also possible to provide a bean of type SentryGraphqlInstrumentation.BeforeSpanCallback which is then used by SentryInstrumenter, e.g.:

  @Bean
  SentryGraphqlInstrumentation.BeforeSpanCallback beforeSpanGraphql() {
    return (
      @NotNull ISpan span, @NotNull DataFetchingEnvironment environment, @Nullable Object result) -> {
      span.setData("beforeSpanCallbackData", "hello world");
      return span;
    };
  }

💡 Motivation and Context

Closes #3412

💚 How did you test it?

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Instructions and example for changelog

Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- Replace `GraphQlSourceBuilderCustomizer` with directly providing a `SentryInstrumenter` bean if missing ([#3744](https://github.com/getsentry/sentry-java/pull/3744))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description.

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