Use general string class and utilities to avoid problems for Google import (#4848)
Use general string class and utilities to avoid problems for Google import (#4848)

Change types used in a new function in access_log_formatter.cc to match other uses in the same
file (and avoid problems for Google import).

Risk Level: Low; no functionality change and minimal code change.

Testing: Existing tests.

Docs Changes: None
Release Notes: None

Signed-off-by: Randy Smith <8692e49a5d99feee623028da27611d5ca92db77f@google.com>
lizan/envoy,jrajahalme/envoy,dnoe/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,lizan/envoy,envoyproxy/envoy,lyft/envoy,lyft/envoy,lizan/envoy,eklitzke/envoy,eklitzke/envoy,jrajahalme/envoy,eklitzke/envoy,istio/envoy,istio/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,lyft/envoy,jrajahalme/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,istio/envoy,dnoe/envoy,dnoe/envoy,envoyproxy/envoy,istio/envoy,lizan/envoy,envoyproxy/envoy-wasm,lizan/envoy,istio/envoy,istio/envoy,envoyproxy/envoy,envoyproxy/envoy,dnoe/envoy,eklitzke/envoy,dnoe/envoy,envoyproxy/envoy-wasm,eklitzke/envoy,jrajahalme/envoy,eklitzke/envoy,lyft/envoy,istio/envoy,lyft/envoy,jrajahalme/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,envoyproxy/envoy,lizan/envoy,jrajahalme/envoy