[GSoC] Functions: Fixes limit evaluations related to trigonometric functions

[sachin-4099]

Fixes: #19770

Brief description of what is fixed or changed

Adds _eval_nseries function to sin and cos.
Adds a piece of code to cos.eval in order to handle the non-zero case.

Other Comments

Regression Tests have been added.

Release Notes

• functions
  • Adds _eval_nseries function to sin and cos.

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• functions
  • Adds _eval_nseries function to sin and cos. (#19916 by @sachin-4099)

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Fixes: #19770

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

Adds `_eval_nseries` function to `sin` and `cos`.
Adds a piece of code to `cos.eval` in order to handle the `non-zero` case.


#### Other Comments
Regression Tests have been added.


#### Release Notes


<!-- BEGIN RELEASE NOTES -->
* functions
  * Adds `_eval_nseries` function to `sin` and `cos`.
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[codecov]

Codecov Report

Merging #19916 into master will increase coverage by 0.034%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master    #19916       +/-   ##
=============================================
+ Coverage   75.778%   75.812%   +0.034%     
=============================================
  Files          668       668               
  Lines       173216    173237       +21     
  Branches     40837     40841        +4     
=============================================
+ Hits        131261    131336       +75     
+ Misses       36221     36174       -47     
+ Partials      5734      5727        -7     

[jksuom]

Thanks, looks good.