[.Net] Update FunctionCallTemplate.tt to encode `"`

[prithvi2226]

Changed the description assigning to handle double quotes in comments and prevent the generated code from breaking.

Why are these changes needed?

When the content in structural comments contains ", the generated code won't get compiled because the " breaks the string.

Modified the FunctionCallTemplate.tt file to properly encode double quotes in descriptions by doubling them. By doubling the double quotes in the description, we ensure that the generated code will compile correctly, even when comments include double quotes.

Related issue number

Closes #2872

Checks

• [x] I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• [x] I've added tests (if relevant) corresponding to the changes introduced in this PR.
• [x] I've made sure all auto checks have passed.

[prithvi2226]

Hi! @LittleLittleCloud , I have updated some changes for your review. Thanks for the support!