Rewrite vCard importer/exporter.

- stop using ServiceConnection inside ImportProcessor/ExportProcessor.
  Just using methods in VCardService would be much less complicated.
- make VCardService responsible for concurrent import/export requests.
  Previously ImportProcessor/ExportProcessor were responsible for them,
  which made the code unnecessary complex.
- use Java concurrent library instead of manually managing requests.
- remove immature test. We need to rewrite it in the future.
- add logs.

Bug: 3064531
Bug: 3188526
Change-Id: I2565d91fb7557d786df42da4b8755cd5311434b9
8 files changed