fix: move tg_connect to general, rustfmt upstream, fix UpstreamManager::new tests

- Relocate tg_connect from [timeouts] to [general] with validation and docs updates.
- Apply rustfmt to per-attempt upstream connect timeout expression in upstream.rs.
- Pass tg_connect_timeout_secs in all UpstreamManager::new test call sites.
- Wire hot reload and runtime snapshot to general.tg_connect.

src/proxy/tests/client_tls_mtproto_fallback_security_tests.rs

@@ -50,6 +50,7 @@ fn build_harness(secret_hex: &str, mask_port: u16) -> PipelineHarness {
         1,
         1,
         1,
+        10,
         1,
         false,
         stats.clone(),