MM-24135: Migrate AppError from SaveChannel/channel_store.go (#14299)

* MM-24135: Migrate AppError from SaveChannel/channel_store.go

This is the first POC of migration of store app errors to plain error.

We create a few basic error types in the store package and use
them to return the errors from store methods. In the app layer,
we inspect the error and re-create the exact app errors. This lets
us preserve the same error content, but yet move to plain errors.

Since this is a gradual migration, this means that the error inspection
code will be duplicated across the app layer whenever a store method
is invoked. But all of that should go away once we start propagating
the errors higher up the hierarchy.

There have been a significant amount of changes in the storetest and searchtest
layer, primarily because we have to rename the err variable now that it is of
a different type.

* Addressed review comments

* Made all appError origins to be CreateChannel

* Remove typed internal error

* Fix translations

* fix layer generation

Co-authored-by: mattermod <mattermod@users.noreply.github.com>

store/searchtest/channel_layer.go

@@ -113,6 +113,7 @@ func testAutocompleteChannelByNameSplittedWithUnderscoreChar(t *testing.T, th *S
 func testAutocompleteChannelByDisplayNameSplittedByWhitespaces(t *testing.T, th *SearchTestHelper) {
 	alternate, err := th.createChannel(th.Team.Id, "channel-alternate", "Channel Alternate", "", model.CHANNEL_OPEN, false)
 	require.Nil(t, err)
+
 	defer th.deleteChannel(alternate)
 	res, apperr := th.Store.Channel().AutocompleteInTeam(th.Team.Id, "Channel A", false)
 	require.Nil(t, apperr)