[Razor] Textmate colorization fixes

[allisonchou]

This is less of a fix and more of a hack. I spent a significant amount of time the past few days trying to fix this the proper way - i.e., making major changes to Razor's Textmate grammar - but it was incredibly frustrating and there were edge cases that kept popping up. This solution fixes the problem without a huge investment but makes some compromises.

Problem:

• The Razor Textmate grammar is very basic and marks a non-trivial amount of proper Razor syntax as invalid.
• VS Code (via language-configuration.json) marks unbalanced brackets in red. Even setting a semantic token type won't override the red color.
• One solution would be to change the grammar to account for certain cases, e.g. recognizing => and " as possible valid syntax in component attributes. But because of how buggy our Razor Textmate grammar already is, this turned out to be a much more difficult task than expected, hence the simplified solution in this PR.
   

Solution:

• Get rid of unbalanced bracket coloring altogether in Razor files. They have a high change of not being accurate since our Textmate grammar isn't great. IMO we could/should eventually use some form of diagnostic to recognize unbalanced brackets instead.
• There is still some red colorization even after these PR changes, which should be resolved after Parentheses after C# transition are classified differently in syntax tree razor#9371 is fixed.

Before example:

After example:

[allisonchou]

We were also missing another semantic classification in our definitions

[allisonchou]

Changing this to be more in line with VS' coloring

[davidwengier]

I think the After picture looks much better