Can't generate correct filename for a specific downloaded image for .tex

Describe the bug
When .rst contain remote image like https://img.shields.io/badge/linux%20kernel-5.1-green, it will generate incorrect file name that can't be parsed by latex,

\noindent{\hspace*{\fill}\sphinxincludegraphics{{test_doc/_build/doctrees/images/83b85f2d6c1db9b7d1e27fc64644d4b3bcab8852/linux%20kernel-5}.1-green}}

Thus make latexpdf would fail.

To Reproduce
Steps to reproduce the behavior:

1. Prepare a .rst file contains the following content

.. image:: https://img.shields.io/badge/linux%20kernel-5.1-green
    :align: right

2. make pdflatex

Runaway argument?
{{test_doc/_build/doctrees/images/83b85f2d6\ETC.
! Paragraph ended before \\sphinxsafeincludegraphics was complete.
<to be read again>
                   \par

Expected behavior

sphinx could generate the correct file name and make latexpdf will succeed.

Environment info

• OS: [e.g. Unix/Linux/Mac/Win/other with version]
• Python version: 3.8
• Sphinx version: 3.0.4
• Sphinx extensions: None

Additional context

I encounter this issue when trying to compile https://github.com/shuveb/loti using sphinx. If this issue is fixed, we need to instruct sphinx to use xelatex to handle some special UTF-8 characters (see #4136) and to use sphinx.ext.imgconverter to include svg images,

extensions = ['manpage', 'sphinx.ext.imgconverter']
latex_engine = 'xelatex'
latex_elements = {}

Reproduce the issue with a .rst image using make latexpdf or make pdflatex, then trace how Sphinx downloads the remote image and derives its filename for LaTeX output. Done means the generated filename does not break at the period in 5.1-green and the LaTeX build succeeds for the provided example.