feat(aggregator): add basic logging

[aasseman]

jsonrpsee already produces a lot of its own logs, so there is no real need to add logs to most of the code (yet?). Use the RUST_LOG environment variable to set the log level.

Fixes #145

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Pull Request Test Coverage Report for Build 5591911064

• 0 of 13 (0.0%) changed or added relevant lines in 1 file are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.6%) to 84.489%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
tap_aggregator/src/main.rs	0	13	0.0%
<!--	Total:	0	13	0.0%	-->

Files with Coverage Reduction	New Missed Lines	%
tap_aggregator/src/main.rs	3	0%
<!--	Total:	3		-->

Totals
Change from base Build 5549295260:	-0.6%
Covered Lines:	975
Relevant Lines:	1154

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