[CDTOOL-1699] Add Log Explorer and Insights CLI commands

[philippschulte]

Change summary

Adds fastly service logging log-explorer and fastly service logging insights commands with service scoping, filtering, pagination, visualization options, JSON/human-readable output, and test coverage.

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[philippschulte]

This pull request depends on fastly/go-fastly#851 and fastly/go-fastly#853.