refactor(comp: timeline): optimize code and style

[liuzaijiang]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added/updated or not needed
• Docs and demo have been added/updated or not needed

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Component style update
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Application (the showcase website) / infrastructure changes
• Other... Please describe:

What is the current behavior?

之前样式不具备扩展性

What is the new behavior?

1. 样式整体全部优化，可以通过修改仅时间轴的点的大小，完全整体视觉修改
2. 通过nth-last-child来优化幽灵节点样式的实现，避免借助js实现
3. 通过background-size实现虚线来代替border，使得虚线视觉可以自己调整

Other information

[idux-bot]

This preview will be available after the AzureCI is passed.

[codecov]

Codecov Report

Merging #819 (9c33b82) into main (0beadd7) will increase coverage by 0.54%.
The diff coverage is 100.00%.

❗ Current head 9c33b82 differs from pull request most recent head 2619537. Consider uploading reports for the commit 2619537 to get more accurate results

@@            Coverage Diff             @@
##             main     #819      +/-   ##
==========================================
+ Coverage   84.88%   85.43%   +0.54%     
==========================================
  Files         493      493              
  Lines       12711    12718       +7     
  Branches     3058     3065       +7     
==========================================
+ Hits        10790    10865      +75     
+ Misses       1921     1853      -68     

Impacted Files	Coverage Δ
packages/components/config/src/defaultConfig.ts	100.00% <ø> (ø)
packages/components/table/src/types.ts	80.00% <ø> (ø)
packages/components/timeline/src/token.ts	100.00% <ø> (ø)
...ackages/components/select/src/trigger/Selector.tsx	93.22% <100.00%> (+1.55%)	⬆️
packages/components/table/src/Table.tsx	100.00% <100.00%> (ø)
...ages/components/table/src/composables/useScroll.ts	88.70% <100.00%> (+0.37%)	⬆️
packages/components/table/src/main/FixedHolder.tsx	83.87% <100.00%> (+74.19%)	⬆️
packages/components/timeline/src/Timeline.tsx	100.00% <100.00%> (ø)
packages/components/timeline/src/TimelineItem.tsx	100.00% <100.00%> (ø)
...ges/components/table/src/composables/useColumns.ts	71.91% <0.00%> (+2.24%)	⬆️
... and 7 more

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