WIP: Support math functions

[travenin]

Work in progress. :gear: :hammer: I want to add some compatibility tests for every function at least.

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Add support for math scalar functions of SQLite: https://sqlite.org/lang_mathfunc.html

Since SQLite CLI and Limbo CLI present floating point numbers with different precision, I added do_execsql_test_tolerance which tests that floating point results close enough of the expected value. However, we probably could make Limbo's floating point presentation match to SQLite.