Opening the same account (context) from multiple processes is dangerous, can result in duplicate
downloads of the same message etc. Same for account manager, attempts to modify the same
accounts.toml even if done atomically with may result in corrupted files as atomic replacement
procedure does not expect that multiple processes may write to the same temporary file.
accounts.toml cannot be used as a lockfile because it is replaced during atomic update. Therefore, a
new file next to accounts.toml is needed to prevent starting second account manager in the same
directory.
But iOS needs to be able to open accounts from multiple processes at the same time. This is required
as the "share-to-DC extension" is a separate process by iOS design -- this process may or may not be
started while the main app is running. Accounts are not altered however by this extension, so let's
add to the `Accounts::new()` constructor an `rdwr` parameter which allows to read the accounts
config w/o locking the lockfile.
get_chat_msgs() function is split into new get_chat_msgs() without flags
and get_chat_msgs_ex() which accepts booleans instead of bitflags.
FFI call dc_get_chat_msgs() is still using bitflags for compatibility.
JSON-RPC calls get_message_ids() and get_message_list_items()
accept booleans instead of bitflags now.
This esp. speeds up receive_imf a bit when we recreate the member list (recreate_member_list == true).
It's a preparation for https://github.com/deltachat/deltachat-core-rust/issues/3768, which will be a one-line-fix, but recreate the member list more often, so that we want to optimize this case a bit.
It also adds a benchmark for this case. It's not that easy to make the benchmark non-flaky, but by closing all other programs and locking the CPU to 1.5GHz it worked. It is consistently a few percent faster than ./without-optim:
```
Receive messages/Receive 100 Chat-Group-Member-{Added|Removed} messages
time: [52.257 ms 52.569 ms 52.941 ms]
change: [-3.5301% -2.6181% -1.6697%] (p = 0.00 < 0.05)
Performance has improved.
Found 7 outliers among 100 measurements (7.00%)
4 (4.00%) high mild
3 (3.00%) high severe
```
All contexts created by the same account manager
share stock string translations. Setting translation on
a single context automatically sets translations for all other
accounts, so it is enough to set translations on the active account.
This allows account manager to construct a single event channel and
inject it into all created contexts instead of aggregating events from
separate event emitters.
