fix(logging): init default retryer

[noahdietz]

Manually copies default retry configuration from the GAPIC WriteLogEntries default call options to be used as the default retry logic for the loggerRetryer. This is what I assume was intended in #7509, but which was not actually done, resulting in the nil panics reported by users (as the defaultRetryer was an uninitialized interface).

Fixes #8408