Repo clean-up for upcoming changes

[Nirmal4G]

Changes

• Remove BOM from new files.
• Remove redundant xml tags and attributes.
• Update Git ignore and attributes.
• Ensure to preserve encoding of UTF-16LE files.
• Update Toolkit Icons and use Icon.png name instead.
• Rename solution, scripts and NuGet config files.
• Remove leftover files from previous refactors.
• Format Notifications package ReadMe.
• Remove redundant code from project files.

PR Type

What kind of change does this PR introduce?

• Code style update (formatting only)
• Refactoring (no functional changes, no API changes)
• Build or CI related changes (non-breaking)

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] Created a separate branch (other than main/master) in your fork
• [x] Based off latest main branch of toolkit
• [x] Pull Request doesn't include merge commits
• [x] Header has been added to all new source files
• [x] Contains NO breaking changes
• [x] Code follows all style conventions

Other information

• Please Rebase merge if possible.
• Please update the default message option to Default to pull request title and description in the Repository Pull Request settings to have a better commit message instead of Merge pull request #xxxx from repo/branch generic message.