fix(metric_logger): expose the logger buffer size in the factory builder (#3541)

* update metric loggers: expose buffer_size through metric logger factory

Signed-off-by: Sahel Sharifymoghaddam <ssharifymogh@nvidia.com>

* validate the passed buffer size at init

Signed-off-by: Sahel Sharifymoghaddam <ssharifymogh@nvidia.com>

* refactor(loggers): single DEFAULT_BUFFER_SIZE constant

The buffer_size default appeared literally in three signatures, so they could
drift apart. Reference one module-level constant instead. No behaviour change.

Signed-off-by: Sahel Sharifymoghaddam <ssharifymogh@nvidia.com>

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Signed-off-by: Sahel Sharifymoghaddam <ssharifymogh@nvidia.com>