feat: Emit ImexProgress(1) after receiving backup size #17452

Job	Run time
Lint Rust	2m 57s
Check if node constants are up to date	4s
cargo deny	39s
Build C library (ubuntu-latest)	2m 29s
Rust doc comments	29s
Check provider database	4s
Build C library (macos-latest)	6m 29s
Python lint	14s
Rust tests (ubuntu-latest, 1.83.0)	3m 9s
Build deltachat-rpc-server (ubuntu-latest)	2m 15s
Rust tests (windows-latest, 1.83.0)	8m 18s
Build deltachat-rpc-server (macos-latest)	2m 51s
Rust tests (macos-latest, 1.83.0)	6m 30s
Rust tests (ubuntu-latest, 1.77.0)	3m 23s
Build deltachat-rpc-server (windows-latest)	18m 58s
CFFI Python tests (ubuntu-latest, 3.13)	5m 3s
CFFI Python tests (macos-latest, 3.13)	3m 49s
CFFI Python tests (ubuntu-latest, pypy3.10)	6m 8s
CFFI Python tests (macos-latest, pypy3.10)	6m 8s
CFFI Python tests (ubuntu-latest, 3.7)	5m 24s
JSON-RPC Python tests (ubuntu-latest, 3.13)	1m 52s
JSON-RPC Python tests (macos-latest, 3.13)	1m 56s
JSON-RPC Python tests (windows-latest, 3.13)	3m 3s
JSON-RPC Python tests (ubuntu-latest, pypy3.10)	2m 10s
JSON-RPC Python tests (macos-latest, pypy3.10)	2m 17s
JSON-RPC Python tests (ubuntu-latest, 3.7)	1m 32s
	1h 38m 11s

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