[dexter] Add keyword argument 'on_line' to DexLabel

Add optional keyword argument 'on_line' to DexLabel to label the specifed line
instead of the line the command is found on.

This will be helpful when used alongside DexDeclareFile (D99651).

Reviewed By: TWeaver

Differential Revision: https://reviews.llvm.org/D101055

GitOrigin-RevId: 487ab5345920b2cfd2162f04b467dd39fb1a8627
4 files changed