[.Net] Update FunctionCallTemplate.tt to encode " (#3068)

* Update FunctionCallTemplate.tt

changed the desscription assigning to handle double quotes in comments and prevent the generated code from breaking.

* Added the necessary changes

Fixed handling of double quotes in descriptions within FunctionCallTemplate.tt.
Standardized newline characters to ensure consistency.
Updated test cases in FunctionCallTemplateEncodingTests to verify correct encoding of double quotes in descriptions.
Cleaned up unnecessary using directives in FunctionCallTemplateEncodingTests.
Aligned the template with the approved test output.

* test cases passing

Test cases passing like `Starting test execution, please wait...
A total of 1 test files matched the specified pattern.

Passed!  - Failed:     0, Passed:     9, Skipped:     0, Total:     9, Duration: 66 ms - AutoGen.SourceGenerator.Tests.dll (net8.0)`

* Delete FunctionCallTemplateTests.TestFunctionCallTemplate.approved.txt

Deleted the ApprovalTests/FunctionCallTemplateTests.TestFunctionCallTemplate.approved.txt successfully!

* Revert "Delete FunctionCallTemplateTests.TestFunctionCallTemplate.approved.txt"

This reverts commit 7a6ea9c.

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Co-authored-by: Xiaoyun Zhang <bigmiao.zhang@gmail.com>