fixed is_integer of Mul by not using fraction but collecting numerators and denominators directly (1.7)

[tbennun]

References to other Issues or PRs

Fixes #20161

Brief description of what is fixed or changed

In Mul._eval_is_integer instead of using the function fraction the args are scanned for contributions to the numerator and denominator.

Other comments

This is a cherry-pick of #20322 pointed towards the 1.7 branch.

Release Notes

• core
  • Fixed a few broken cases of expr.is_integer

[sympy-bot]

✅

Hi, I am the SymPy bot (v161). I'm here to help you write a release notes entry. Please read the guide on how to write release notes.

Your release notes are in good order.

Here is what the release notes will look like:

• core
  • Fixed a few broken cases of expr.is_integer (#20450 by @coproc and @tbennun)

This will be added to https://github.com/sympy/sympy/wiki/Release-Notes-for-1.7.

Click here to see the pull request description that was parsed.

<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->

#### References to other Issues or PRs
Fixes #20161

#### Brief description of what is fixed or changed
In Mul._eval_is_integer instead of using the function fraction the args are scanned for contributions to the numerator and denominator.


#### Other comments

This is a cherry-pick of #20322 pointed towards the `1.7` branch.

#### Release Notes

<!-- Write the release notes for this release below. See
https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more information
on how to write release notes. The bot will check your release notes
automatically to see if they are formatted correctly. -->

<!-- BEGIN RELEASE NOTES -->
* core
  * Fixed a few broken cases of expr.is_integer
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[codecov]

Codecov Report

Merging #20450 (73f3d75) into 1.7 (9e7ae94) will increase coverage by 0.000%.
The diff coverage is 100.000%.

@@            Coverage Diff            @@
##               1.7    #20450   +/-   ##
=========================================
  Coverage   75.703%   75.704%           
=========================================
  Files          674       674           
  Lines       174162    174175   +13     
  Branches     41098     41103    +5     
=========================================
+ Hits        131847    131858   +11     
- Misses       36565     36569    +4     
+ Partials      5750      5748    -2     

[oscarbenjamin]

Thanks. This looks good!