make scoped logger work with logger objects with non-int level

[HoneyryderChuck]

What was changed

This patch fixes scoped loggers by allowing a escape hatch for logger objects with non-integer levels; just call #upcase (which both strings and symbols support) and pass it to Logger::Severity.const_get.

Why?

Logger#level returns an integer, however many other logger libraries in ruby land don't do that, most notably semantic_logger, which is nowadays recommended by rails for structured logging; SemanticLogger::Logger objects return #level as a symbol (ex: :info).

Checklist

1. Closes [Bug] Does not support semantic_logger #472

2. How was this tested:

require "semantic_logger"
require "temporalio"

logger = SemanticLogger["MyApp"]
scoped_logger = ScopedLogger.new(logger)
scoped_logger.level #=> 1, 2 ,3....

3. Any docs updates needed?

Don't think so, temporalio does not document support for logger libs.

[CLAassistant]

All committers have signed the CLA.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}