GH-45250: [JS] Fix denominator precision loss and remove unnecessary safe integer check for fractional part

[yaooqinn]

Rationale for this change

What changes are included in this PR?

This PR uses string constructor for bigint to calculate the power of 10 with scale as the exponent value of the expression.

To Fix precision loss like

> BigInt(10) ** BigInt(25);
10000000000000000000000000n
> BigInt(Math.pow(10, 25))
10000000000000000905969664n

Also, we remove the unnecessary safe integer check for the fraction part.

Are these changes tested?

add some unit tests

Are there any user-facing changes?

no

• GitHub Issue: bigNumToNumber method may result precision loss for denominator calculation #45250

[github-actions]

Thanks for opening a pull request!

If this is not a minor PR. Could you open an issue for this pull request on GitHub? https://github.com/apache/arrow/issues/new/choose

Opening GitHub issues ahead of time contributes to the Openness of the Apache Arrow project.

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

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

or

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

See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[github-actions]

⚠️ GitHub issue #45250 has been automatically assigned in GitHub to PR creator.

[yaooqinn]

Thank you @trxcllnt for the suggestion and approval.

[domoritz]

Thank you!

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 4 benchmarking runs that have been run so far on merge-commit f8f17a5.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 20 possible false positives for unstable benchmarks that are known to sometimes produce them.