…y batch is present (#1866)

Reproduces and fixes: #1847 

Parquet files with empty row groups are valid per the spec, but
Snowflake does not currently handle them properly. To mitigate this we
buffer writes to the parquet file so that a row group is not written
until some amount of data has been received.

The CheckedAllocator was enabled for all tests as part of this fix,
which detected a leak in the BufferWriter that was fixed in:
[https://github.com/apache/arrow/pull/41698](https://github.com/apache/arrow/pull/41698).

There was an unrelated test failure that surfaced once the
CheckedAllocator was enabled which had to do with casting decimals of
certain precision. The fix is included in this PR as well.

…riter is closed (apache#41698)

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Then could you also rename the pull request title in the following
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    GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

    MINOR: [${COMPONENT}] ${SUMMARY}

In the case of PARQUET issues on JIRA the title also supports:

    PARQUET-${JIRA_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

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### Rationale for this change

A small buffer gets reallocated after calling `Finish()`, causing that
memory to leak.

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Release the buffer when the pagewriter is closed.

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…riter is closed (apache#41698)

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Then could you also rename the pull request title in the following
format?

    GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

    MINOR: [${COMPONENT}] ${SUMMARY}

In the case of PARQUET issues on JIRA the title also supports:

    PARQUET-${JIRA_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

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### Rationale for this change

A small buffer gets reallocated after calling `Finish()`, causing that
memory to leak.

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### What changes are included in this PR?
Release the buffer when the pagewriter is closed.

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…riter is closed (apache#41698)

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Then could you also rename the pull request title in the following
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    GH-${GITHUB_ISSUE_ID}: [${COMPONENT}] ${SUMMARY}

or

    MINOR: [${COMPONENT}] ${SUMMARY}

In the case of PARQUET issues on JIRA the title also supports:

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### Rationale for this change

A small buffer gets reallocated after calling `Finish()`, causing that
memory to leak.

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in the issue then this section is not needed.
Explaining clearly why changes are proposed helps reviewers understand
your changes and offer better suggestions for fixes.
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### What changes are included in this PR?
Release the buffer when the pagewriter is closed.

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is sometimes worth providing a summary of the individual changes in this
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### Are these changes tested?
Yes

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* GitHub Issue: apache#41697