[C++][Gandiva] Add LTRIM, RTRIM, BTRIM functions for string

[asfimport]

Reporter: Sagnik Chakraborty / @sgnkc
Assignee: Sagnik Chakraborty / @sgnkc

PRs and other links:

• GitHub Pull Request #7641

_{Note: This issue was originally created as ARROW-9328. Please see the migration documentation for further details.}

[asfimport]

Praveen Kumar / @praveenbingo:
Issue resolved by pull request 7641
#7641