Send multiple event in batches

[zmoog]

Motivation

We want to send more than one event with a single command.

For example, given the multiline.txt file contains multiple lines:

$ cat multiline.txt
line 1
line 2
line 3

We want to send all of these lines to event hub in a single batch using one of the following options:

# reading the lines from a file:
$ eh eventdata send --lines-from-text-file multiline.txt
line 1
line 2
line 3

# or using the standard input:
$ cat multiline.txt | eh eventdata send
line 1
line 2
line 3

Change description

Switch from using send_event(event) to send_batch(batch) on EventHubProducerClient.

We currently support str-based inputs only, so no bytes content at the moment.

Additional Notes

• Closes Send eventdata using batches #2

Reviewer checklist

• PR address a single concern.
• PR title and description are appropriately filled.
• Changes will be merged in main.
• Changes are covered by tests.
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