add trimChar option in database reader to trim the space of char type in database

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

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Files	Coverage Δ
datax/plugin/writer/dbms/task.go	`100.00% <100.00%> (ø)`
storage/database/config.go	`100.00% <100.00%> (ø)`
storage/database/db2/field.go	`97.74% <100.00%> (+0.05%)`	:arrow_up:
storage/database/db2/table.go	`100.00% <100.00%> (ø)`
storage/database/mysql/field.go	`100.00% <100.00%> (ø)`
storage/database/mysql/table.go	`100.00% <100.00%> (ø)`
storage/database/oracle/field.go	`100.00% <100.00%> (ø)`
storage/database/oracle/table.go	`100.00% <100.00%> (ø)`
storage/database/postgres/field.go	`100.00% <100.00%> (ø)`
storage/database/postgres/table.go	`100.00% <100.00%> (ø)`
... and 4 more

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