Rate limiter for LLM clients

Grammars written for ANTLR v4; expectation that the grammars are free of actions.

ANTLR (ANother Tool for Language Recognition) is a powerful parser generator for reading, processing, executing, or translating structured text or binary files.

Statistical Machine Intelligence & Learning Engine

antlr v3 repository (pulled from p4 with history from //depot/code/antlr/antlr3-main

antlr v3 repository (pulled from p4 with history from //depot/code/antlr/antlr3-main

StringTemplate 4