avoid chrono dependency, depend on proxmox 0.3.8

- remove chrono dependency

- depend on proxmox 0.3.8

- remove epoch_now, epoch_now_u64 and epoch_now_f64

- remove tm_editor (moved to proxmox crate)

- use new helpers from proxmox 0.3.8
  * epoch_i64 and epoch_f64
  * parse_rfc3339
  * epoch_to_rfc3339_utc
  * strftime_local

- BackupDir changes:
  * store epoch and rfc3339 string instead of DateTime
  * backup_time_to_string now return a Result
  * remove unnecessary TryFrom<(BackupGroup, i64)> for BackupDir

- DynamicIndexHeader: change ctime to i64

- FixedIndexHeader: change ctime to i64

src/api2/status.rs

@@ -23,7 +23,6 @@ use crate::api2::types::{
 use crate::server;
 use crate::backup::{DataStore};
 use crate::config::datastore;
-use crate::tools::epoch_now_f64;
 use crate::tools::statistics::{linear_regression};
 use crate::config::cached_user_info::CachedUserInfo;
 use crate::config::acl::{
@@ -110,7 +109,7 @@ fn datastore_status(
         });
 
         let rrd_dir = format!("datastore/{}", store);
-        let now = epoch_now_f64()?;
+        let now = proxmox::tools::time::epoch_f64();
         let rrd_resolution = RRDTimeFrameResolution::Month;
         let rrd_mode = RRDMode::Average;