Unevaluated collect with symbols in factors

[mloubout]

References to other Issues or PRs

Fixes #19433

Brief description of what is fixed or changed

This PR fixes a small issue in collect with the collected symbol in the factor. Current version does:

>> from sympy import symbol, collect
>> a = symbols('a')
>> collect(a**2*(a**2 + 1), a**2, evaluate=False)
{a**2: _Dummy_20 + 1}

that contains an undefined Dummy in the collected expression,. This fixes the behavior applying replacement to the factors and outputs in this example.

{a**2: a**2 + 1}

Other comments

Release Notes

• simplify
  • Fixes a bug in collect when collected symbols appear in the facorized expression.

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• simplify
  • Fixes a bug in collect when collected symbols appear in the facorized expression. (#19431 by @mloubout)

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#### References to other Issues or PRs
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Fixes #19433

#### Brief description of what is fixed or changed

This PR  fixes a small issue in `collect` with the collected symbol in the factor. Current version does:
```
>> from sympy import symbol, collect
>> a = symbols('a')
>> collect(a**2*(a**2 + 1), a**2, evaluate=False)
{a**2: _Dummy_20 + 1}
```
that contains an undefined `Dummy` in the collected expression,. This fixes the behavior applying replacement to the factors and outputs in this example.
```
{a**2: a**2 + 1}
```
#### Other comments


#### Release Notes

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on how to write release notes. The bot will check your release notes
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<!-- BEGIN RELEASE NOTES -->

* simplify
    * Fixes a bug in collect when collected symbols appear in the facorized expression.

<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[smichr]

Looks good. Ready to merge when tests pass.

[codecov]

Codecov Report

Merging #19431 into master will increase coverage by 0.001%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master    #19431       +/-   ##
=============================================
+ Coverage   75.651%   75.653%   +0.001%     
=============================================
  Files          652       652               
  Lines       169712    169712               
  Branches     40051     40051               
=============================================
+ Hits        128390    128393        +3     
+ Misses       35720     35714        -6     
- Partials      5602      5605        +3     

[smichr]

Thanks, this is in.