Loggo2

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- Upgraded typing-extensions to be >=4.2.0,<5.0.0
- Needed for Solana compatibility in index-to-address
- Removing Python < 3.9
- Adding Github Actions checks to run test suite
- Minor fixes to previously failing tests

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- Fixed
- Set as Optional a type initialized to None

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- Changed
- "Returned from" log message is now more concise.

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- Changed
- Set default log level to `INFO`

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- Changed
- Package renamed from `loggo` to `loggo2`

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- Added
- Make Loggo init accept a new optional parameter log_formatter, which specifies a formatter used while writing log records to stdout or a file. Loggo remains backward compatible, as the default log formatter is LocalLogFormatter.
- Add a new log formatter JsonLogFormatter
- Changed
- `private_data` kwarg of `Loggo.__init__` no longer accepts `None` value.