[MLOB-5481] feat: add basic mcp server with tool to query llmobs span events

[sabrenner]

adds a basic in-house mcp server to query llmobs span events with a basic filter pattern (without needing to specify datadog query syntax).

• has a basic dev tooling for adding new tools without needing to specify all functions out specifically, they are interpreted from how they are implemented (needing docstrings, etc.)
• implements a get_llmobs_span_events tool with filters to limit context usage for agents

follow-ups/improvements

• tool for querying custom evaluation metrics (might require joining, we should implement it first for the llmobs platform in general so it can be used on the frontend)
• add some tests (?)