Part of #1724.

In this PR, we add support for using a query parameter of RANGE type, either named or positional. Here is an example below:

from google.cloud import bigquery
from datetime import datetime, date

# Construct a BigQuery client object.
client = bigquery.Client()

query = """SELECT ? AS foo"""


# Set the name to None to use positional parameters.
# Note that you cannot mix named and positional parameters.
job_config = bigquery.QueryJobConfig(
    query_parameters=[
        bigquery.RangeQueryParameter("DATETIME", start=datetime(year=2020, month=10, day=30), end=None),
    ]
)

results = client.query_and_wait(query, job_config=job_config) 

for row in results:
    print(row)

More specifically:

• Added classes RangeQueryParameter, RangeQueryParameterType and their corresponding methods
• Added unit tests
• Added system tests

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Towards #1724 🦕