Use `size_t` instead of `uint32_t` in `vespalib::GrowStrategy`
Use `size_t` instead of `uint32_t` in `vespalib::GrowStrategy`

vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa,vespa-engine/vespa