[lldb] Add tree-sitter based syntax highlighting (#181279)
This adds the necessary infrastructure to use tree-sitter for syntax
highlighting in LLDB. It provides the base class for a tree-sitter
highlighter plugin. Its primary function is interfacing with the
tree-sitter library, and converting captures to highlighting styles.
Adding a new tree-sitter highlighter consists of creating an LLDB plugin
that inherits from this class. The plugin has two core responsibilities:
1. Loading the tree-sitter grammar.
2. Specifying the tree-sitter syntax highlighting query.
Everything else is handled by the base class, making it extremely easy
to add a new language.
For more context and the motivation behind using tree-sitter for syntax
highlighting, see #170250.
