945062: Enum Filtering, Excel exporting, Pdf Exporting

[NithyaSivaprakasam]

In this PR, three topics have been added for the ASP.NET Core and MVC platforms:

1. Perform Enum filtering
2. Show/Hide columns while exporting to Excel with a stacked header
3. Show/Hide columns while exporting to PDF with a stacked header

[SyncfusionBuild]

The running CI Job is terminated due to changes committed on the source branch for this Merge Request and CI triggered for latest commit.

[SyncfusionBuild]

CI Status: ABORTED ❌
Source Compilation: Not Started ❌
Build Location: 945062-fetch-part1-hotfix

[SyncfusionBuild]

Build Status: INPROGRESS 🔃
Build Location: 945062-fetch-part1-hotfix

[SyncfusionBuild]

CI Status: SUCCESS ✅
Source Compilation: SUCCESS ✅
Build Location: 945062-fetch-part1-hotfix
Image Alt Text Error(s): 0
Image Size Error(s): 0
Image Name Error(s): 0
FT Layout Syntax Error(s): 0
Front matter Error(s): 0
File Path Error(s): 0
CodeSnippet File Path Missing Error(s): 0
Toc Anchor Tags Validation Error(s): 0
MD Tag Validation Error(s): 0

[SyncfusionBuild]

Build Status: INPROGRESS 🔃
Build Location: 945062-fetch-part1-hotfix

[SyncfusionBuild]

CI Status: SUCCESS ✅
Source Compilation: SUCCESS ✅
Build Location: 945062-fetch-part1-hotfix
Image Alt Text Error(s): 0
Image Size Error(s): 0
Image Name Error(s): 0
FT Layout Syntax Error(s): 0
Front matter Error(s): 0
File Path Error(s): 0
CodeSnippet File Path Missing Error(s): 0
Toc Anchor Tags Validation Error(s): 0
MD Tag Validation Error(s): 0