Add argument `wait` of `remove_job` and `remove_all_jobs`

### Things to check first

- [X] I have searched the existing issues and didn't find my feature already requested there

### Feature description

`remove_job` or `remove_all_jobs` of `BackgroundScheduler` should block when there is still running jobs, such as `shutdown(wait=True)`.

### Use case

Without blocking:
```python
import time

from apscheduler.schedulers.background import BackgroundScheduler

def count(arr):
time.sleep(0.2)
arr[0] += 1

if __name__ == '__main__':
# Scheduler with 5 workers
gconfig = {
'apscheduler.job_defaults.max_instances': 5
}
scheduler = BackgroundScheduler(gconfig)

# The job is increment the first element every 0.1 seconds
# Each increment requires 0.2 seconds
arr = [0]
scheduler.add_job(
count,
'interval',
seconds=0.1,
args=(arr,)
)
scheduler.start()

# Do the jobs in a second
time.sleep(1.0)

print('Value', arr[0]) # Value 7

# Remove the jobs and reset the value
scheduler.remove_all_jobs()
arr[0] = 0

# However, as it is not blocked, there's still running jobs, the value keeps incrementing
time.sleep(1.0)
print('Value', arr[0]) # Value 2
```
With blocking:
```python
import time

from apscheduler.schedulers.background import BackgroundScheduler

def count(arr):
time.sleep(0.2)
arr[0] += 1

if __name__ == '__main__':
# Scheduler with 5 workers
gconfig = {
'apscheduler.job_defaults.max_instances': 5
}
scheduler = BackgroundScheduler(gconfig)

# The job is increment the first element every 0.1 seconds
# Each increment requires 0.2 seconds
arr = [0]
scheduler.add_job(
count,
'interval',
seconds=0.1,
args=(arr,)
)
scheduler.start()

# Do the jobs in a second
time.sleep(1.0)

print('Value', arr[0]) # Value 7

# Remove the jobs and reset the value
scheduler.remove_all_jobs(wait=True)
arr[0] = 0

# The value is reset after all jobs are removed, it keeps 0
time.sleep(1.0)
print('Value', arr[0]) # Value 0
```