fix(slider): 修改 slider 的最大值最小值 位置 计算数据方式 floor 为 round

[ai-qing-hai]

修改 slider 的最大值最小值 位置 计算数据方式 floor 为 round

before	after

fixed #3853

[github-actions]

🎊 PR Preview b923eb3 has been successfully built and deployed to https://antvis-G2-preview-pr-4015.surge.sh?type=diff&date=2022-06-29

🕐 Build time: 85.849s

_{🤖 By Surge Ui Insight}

[coveralls]

Pull Request Test Coverage Report for Build 2582125031

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.006%) to 91.265%

---

Totals
Change from base Build 2573335166:	0.006%
Covered Lines:	11820
Relevant Lines:	12458

---

💛 - Coveralls

[hustcc]

如果改成 float 之后，滑动条在最右方的时候，可以选择到最后一条数据吗？

[visiky]

如果改成 float 之后，滑动条在最右方的时候，可以选择到最后一条数据吗？

是修改为 round（不是floor）