feat: Emit ImexProgress(1) after receiving backup size #17454

Job	Run time
Build C library (ubuntu-latest)	2m 23s
Build C library (macos-latest)	2m 57s
cargo deny	33s
Rust doc comments	20s
Lint Rust	2m 38s
Check if node constants are up to date	3s
Check provider database	6s
Python lint	12s
Rust tests (ubuntu-latest, 1.83.0)	3m 14s
Rust tests (windows-latest, 1.83.0)	8m 15s
Rust tests (macos-latest, 1.83.0)	3m 10s
Build deltachat-rpc-server (ubuntu-latest)	2m 5s
Rust tests (ubuntu-latest, 1.77.0)	3m 22s
Build deltachat-rpc-server (macos-latest)	3m 3s
Build deltachat-rpc-server (windows-latest)	8m 56s
CFFI Python tests (ubuntu-latest, 3.13)	6m 52s
CFFI Python tests (macos-latest, 3.13)	4m 45s
CFFI Python tests (ubuntu-latest, pypy3.10)	7m 37s
CFFI Python tests (macos-latest, pypy3.10)	5m 54s
CFFI Python tests (ubuntu-latest, 3.7)	6m 50s
JSON-RPC Python tests (ubuntu-latest, 3.13)	1m 44s
JSON-RPC Python tests (macos-latest, 3.13)	2m 22s
JSON-RPC Python tests (windows-latest, 3.13)	3m 2s
JSON-RPC Python tests (ubuntu-latest, pypy3.10)	1m 49s
JSON-RPC Python tests (macos-latest, pypy3.10)	2m 11s
JSON-RPC Python tests (ubuntu-latest, 3.7)	1m 38s
	1h 26m 1s

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