Fixes writer max annotation option doesn't work.

[cheqianh]

Description:

This PR is working on amazon-ion/ion-python#165 on ion-c layer and the fix of ion-python layer is here.

Step by step fix:

1. The writer option's max annotation count is set when writer is initialized but never used. For example, I set max annotation count to 100 but it still writes at most 10 annotations.
2. The root is because the writer always set annotations counts to default (10) when a writer writes the first annotation no matter how much we set for max_annotation_count. Code details is here. Changed it to max_annotation_count as below (line 1099).
3. Then it raise an IERR_NO_MEMORY error when max_annotation_count is so large. The root is because we only allocate default memory (In this case, it's 1024 bytes) for temp_buffer where the annotation bytes is stored. The code details is here. So I calculated how much bytes we need for annotations:
   p_options->max_annotation_count * sizeof(ION_SYMBOL)
4. However, above three steps fix the ion-hash issue but fail some ion-c unit test. This is because the temp_buffer is not only used for annotation. For example, ion_writer_text reserved bytes from temp buffer twice. So, for example, if there are 100 bytes for annotations, we need to allocate more than 100 bytes for temp_buffer because it will be used somewhere else too.
5. So I separate the annotation calculation from the defaults bytes. I allocate p_options->max_annotation_count * sizeof(ION_SYMBOL) + ION_WRITER_TEMP_BUFFER_DEFAULT bytes for temp_buffer (see change below line 278) where it has +ION_WRITER_TEMP_BUFFER_DEFAULT at the end. So we calculate how many bytes annotations need first, then add ION_WRITER_TEMP_BUFFER_DEFAULT for other fields, which solves the issue and passes all tests.
6. Here might be a minor improvement. Before we allocate 1024 bytes for everything but now we separate annotations and other fields so it doesn't need default to 1024 bytes anymore. I think we can decrease the default value to 512 and add some comments explaining why.

Tests:

This change passes ion-c tests, ion-python tests and ion-hash-python tests.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.