Truncate the given userdata_exp alias partition

Given userdata.alias.remove prop by vendors, userdata_alias_remove service
will truncate the below file for giving back the space to userdata. The
target file names should exactly match with one of alias file names in
userdata.alias.devices created by fs_mgr.

/data/${userdata.alias.remove}

Bug: 383008495
Bug: 378120929
Test: trigger file truncation by vendors
Change-Id: Ie0b3c0476893bf5593f01588707568b7c8a102f2
Signed-off-by: Daeho Jeong <daehojeong@google.com>