Improve wording for queries and DB descriptions

[shreyashankar]

The queries are awesome!!

This PR addresses grammar, clarity, and ambiguity issues in query files and database descriptions across all query
datasets.

Key changes:

• Made queries unambiguous with clear instructions
• Fixed grammar issues and standardized terminology in database descriptions
• Centralized duplicate db_description.txt files into single files per dataset
• Improved hints with clearer explanations

Outstanding issues to address:

1. Vague hints in Yelp dataset: The hint "The datasets contain five tables total. Carefully identify which tables and columns contain the information required to answer the query" should specify which tables are needed for each query type.
2. MongoDB symbol definitions: The stockmarket_symboldefinition/SymbolDirectoryDefinitions.bson file should be converted to text format & included in the hint directly or provided as a proper database connection, like the other databases.
3. Missing ground truth validation: Though there are ground truth query scripts, we should have a file of all query answers and validation functions to check whether an agent's predicted answer is correct. For example, if the answer is a list of companies and quantities, the function should check that each company and quantity is present in the agent's string response.