[GSoC]Change return type of P and E with evaluate=False

[Smit-create]

References to other Issues or PRs

Fixes #19798

Brief description of what is fixed or changed

Change in the return types of P and E with evaluate=False. Examples:

>>> from sympy.stats import *
>>> X = Normal('X',1,2)
>>> P(X > 1, evaluate=False)
Probability(X > 1)
>>> E(X, evaluate=False)
Expectation(X)

Other comments

Release Notes

• stats
  • Change in return type of P and E with evaluate=False. With evaluate=False, P and E are made to return Probability and Expectation object respectively.

ping @czgdp1807 @Upabjojr @jmig5776

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• stats
  • Change in return type of P and E with evaluate=False. With evaluate=False, P and E are made to return Probability and Expectation object respectively. (#19819 by @Smit-create)

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was changed. Do not include the issue number in the title. -->

#### References to other Issues or PRs
<!-- If this pull request fixes an issue, write "Fixes #NNNN" in that exact
format, e.g. "Fixes #1234" (see
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Fixes #19798

#### Brief description of what is fixed or changed
Change in the return types of P and E with `evaluate=False`. Examples:
```py
>>> from sympy.stats import *
>>> X = Normal('X',1,2)
>>> P(X > 1, evaluate=False)
Probability(X > 1)
>>> E(X, evaluate=False)
Expectation(X)
```

#### Other comments


#### Release Notes

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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
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<!-- BEGIN RELEASE NOTES -->
* stats
   * Change in return type of `P` and `E` with `evaluate=False`. With `evaluate=False`, `P` and `E` are made to return `Probability` and `Expectation` object respectively.
<!-- END RELEASE NOTES -->
ping @czgdp1807 @Upabjojr @jmig5776 

Update

The release notes on the wiki have been updated.

[codecov]

Codecov Report

Merging #19819 into master will increase coverage by 0.008%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master    #19819       +/-   ##
=============================================
+ Coverage   75.722%   75.730%   +0.008%     
=============================================
  Files          664       664               
  Lines       172376    172483      +107     
  Branches     40653     40678       +25     
=============================================
+ Hits        130527    130623       +96     
- Misses       36146     36158       +12     
+ Partials      5703      5702        -1     

[Smit-create]

@czgdp1807 @Upabjojr Please have a look if it looks good to merge.

[czgdp1807]

LGTM. @Upabjojr Should we merge this?