fix(swiper): refactor user scrolling judgment by touch angle

[xxyan0205]

背景描述

是否用户滚动页面行为的判断存在问题，无法区分touchmove轨迹“拐弯”的情况，会造成无法正常翻页#540

主要改动

重写$_isScroll方法，根据滚动夹角判断是否用户滚动页面行为

需要注意

是否阻塞正常滚动

[codecov-io]

Codecov Report

Merging #541 into dev will decrease coverage by 0.31%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##              dev     #541      +/-   ##
==========================================
- Coverage   81.16%   80.84%   -0.32%     
==========================================
  Files          91       91              
  Lines        2723     2725       +2     
  Branches      522      526       +4     
==========================================
- Hits         2210     2203       -7     
- Misses        367      372       +5     
- Partials      146      150       +4

Impacted Files	Coverage Δ
components/swiper/index.vue	64.57% <50%> (-2.62%)	⬇️

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