Range gives inconsistent results for month end

[jadchaar]

Issue Description

env ❯ python3
Python 3.8.5 (default, Jul 21 2020, 10:48:26)
[Clang 11.0.3 (clang-1103.0.32.62)] on darwin
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>>> import arrow
>>> from datetime import datetime
>>> start_date = datetime(2014, 12, 31)
>>> list(arrow.Arrow.range("month", start_date, limit=5))
[<Arrow [2014-12-31T00:00:00+00:00]>, <Arrow [2015-01-31T00:00:00+00:00]>, <Arrow [2015-02-28T00:00:00+00:00]>, <Arrow [2015-03-28T00:00:00+00:00]>, <Arrow [2015-04-28T00:00:00+00:00]>

When months in a range end on different dates (e.g. January and February), the range seems to continue with the end date of the previous month.

System Info

• 🖥 OS name and version: macOS 10.15.6
• 🐍 Python version: 3.8.5
• 🏹 Arrow version: 0.15.8

[jadchaar]

This issue may occur as well with years since leap years can increase the number of days in a year.

[systemcatch]

Fixed in #844