* test/api/*.vala: Renamed files that contained mock objects to *-mock.vala,
not *-test.vala.
* test/testcase.vala: Renamed to test-case.vala for consistency, remove
TestCase class from Gee package since that's really not true. Clean up
code for consistency.
* test/meson.build, test/CMakeLists.txt: Split TestCase compilation out
into a separate test lib.
This generalises the approach used to execute the flag watcher and
background sync, provides a high-level means of managing local and remote
operations, and provides a means of compartmentalising operation-specific
code.
* src/engine/imap-engine/imap-engine-account-operation.vala
(AccountProcessor): Interface for denoting classes that implements some
account-specific operation.
* src/engine/imap-engine/imap-engine-account-processor.vala
(AccountProcessor): Class to manage the operation queue and execute
operations.
* src/engine/imap-engine/imap-engine-generic-account.vala
(GenericAccount): Create and manage an instance of AccountProcessor,
add queue_operation method to allow operations to be queued.
