[lldb-vscode ]Add Syntax Highlighting to Disassembly View

When lldb cannot find source file thus IDE renders a disassembly view, add syntax highlighting for constants, registers and final line comments for better debugging experience.
The original plain disassembly view looks like:
{F12401687}
An ideal view is like the screenshot attached.
{F12401515}

In this diff, the mimeType is a kind of media type for formatting the content in the response to a source request. Elements in the disassembly view, like constants, registers and final line comments are colored for highlighting.
A built-in support in the VSCode IDE for syntax highlighting will identify the which mimeType to apply and render the disassembly view as expected.

Reviewed By: wallace, clayborg

Differential Revision: https://reviews.llvm.org/D84555