Improve handling UTF encoded inputs

[fktn-k]

This PR has improved the way of handling UTF encoded inputs by:

• dropping information about the existence of a byte order mark (BOM) from inputs during the creation of an input adapter object since the information won't be needed by the lexer and the deserializer, and
• preparing a normalized input buffer which is guranteed to be encoded in the UTF-8 format in the input_handler class before the actual start of the deserialization process.

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Pull Request Checklist

Read the CONTRIBUTING.md file for detailed information.

• [x] Changes are described in the pull request or in a referenced issue.
• [x] The test suite compiles and runs without any error.
• [x] The code coverage on your branch is 100%.
• [x] The documentation is updated if you added/changed a feature.

Please don't

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[coveralls]

Pull Request Test Coverage Report for Build 8407932666

Details

• 184 of 184 (100.0%) changed or added relevant lines in 6 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 8407215565:	0.0%
Covered Lines:	2936
Relevant Lines:	2936

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💛 - Coveralls

[fktn-k]

Waiting for #293 to get merged to avoid conflicts on that branch due to the changes with lower priority.