Support typed dynamic filter metadata in access loggers

[nezdolik]

Title: Support typed dynamic filter metadata in access loggers

Description:
Nowadays access logger supports formatters for dynamic filter metadata, e.g. %DYNAMIC_METADATA(NAMESPACE:KEY*):Z%, but as the adoption of typed filter metadata will increase across Envoy filters, we need to introduce support for typed filter metadata in the access logger extension.

Relevant Links
Current use case where proxy protocol filter sets typed filter metadata and could benefit from access logger's support for such type of data.

[phlax]

cc @ggreenway @soulxu

[cpakulski]

So, the goal is to "understand" a syntax of typed dynamic metadata, correct? In other words, the formatter should know how to display a dynamic metadata based on its type, instead of dumping that metadata in generic way.

Btw, there is new METADATA formatter: https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/formatter/metadata/v3/metadata.proto#envoy-v3-api-msg-extensions-formatter-metadata-v3-metadata, which I put as an extension, but am planning to bring it back into core as core formatter. That new formatter will eventuall obsolete multiple *_METADATA formatters: #33004.