internal/controller: add exponential backoff

[datdao]

This PR replaces the retry mechanism for errors from a fixed 5-second interval to an exponential backoff strategy. The delay is now calculated base on the number of failures for each resource.

A backoffLimit field has been added to the spec to configure the maximum number of retries. By default, it is set to 20. If backoffLimit is set to 0, retries will be unlimited.

When the number of retries exceeds the backoffLimit, the controller will log an event to notify about this.

Example of setting backoffLimit for AtlasMigration and Atlas Schema resources:

apiVersion: db.atlasgo.io/v1alpha1
kind: AtlasMigration
metadata:
  name: mysql
spec:
  backoffLimit: 5
  dir:
    configMapRef:
      name: "migration-dir"
---
apiVersion: db.atlasgo.io/v1alpha1
kind: AtlasSchema
metadata:
  name: mysql
spec:
  backoffLimit: 5
  schema:
    sql: |
      create table users (
        id int not null auto_increment,
        name varchar(255) not null,
        email varchar(255) unique not null,
        short_bio varchar(255) not null,
        primary key (id)
      );