Fix linting issues with numpy 2

Description of changes:

Seeing the error below on CI/CD linting:

home/runner/work/streaming/streaming/streaming/base/spanner.py:59:35 - error: Argument of type "NDArray[signedinteger[Any]]" cannot be assigned to parameter "__x" of type "ReadableBuffer | str | SupportsInt | SupportsIndex | SupportsTrunc" in function "__new__"
    Type "NDArray[signedinteger[Any]]" cannot be assigned to type "ReadableBuffer | str | SupportsInt | SupportsIndex | SupportsTrunc"
      "NDArray[signedinteger[Any]]" is incompatible with "str"
      "NDArray[signedinteger[Any]]" is incompatible with "ReadOnlyBuffer"
      "NDArray[signedinteger[Any]]" is incompatible with "bytearray"
      "NDArray[signedinteger[Any]]" is incompatible with "memoryview"
      "NDArray[signedinteger[Any]]" is incompatible with "array[Any]"
      "NDArray[signedinteger[Any]]" is incompatible with "mmap"
      "NDArray[signedinteger[Any]]" is incompatible with "_CData" (reportGeneralTypeIssues)

This seems to be an issue with the numpy upgrade and typing for casting to ints. We cast to int explicitly using .item() to address the typing issue.

The second error is:

/home/runner/work/streaming/streaming/streaming/base/shared/prefix.py:121:42 - error: "in1d" is not a known member of module (reportGeneralTypeIssues)

Which is happening because np.in1d is deprecated in numpy 2, in favor of np.isin (see here). We simply replace the call with np.isin.

Issue #, if available:

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mosaicml / streaming