Add bar chart bottom tooltip for `fromY` value

[sownt]

Related issue #1389

[codecov[bot]]

Codecov Report

Attention: 78 lines in your changes are missing coverage. Please review.

Comparison is base (e9ab493) 86.72% compared to head (2fb090e) 84.56%.

Files	Patch %	Lines
lib/src/chart/bar_chart/bar_chart_painter.dart	7.14%	78 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1521      +/-   ##
==========================================
- Coverage   86.72%   84.56%   -2.16%     
==========================================
  Files          45       45              
  Lines        3020     3104      +84     
==========================================
+ Hits         2619     2625       +6     
- Misses        401      479      +78     

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[imaNNeo]

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