Tracking issue: Add Log Namespace support to sinks

[fuchsnj]

Sinks need updated to work correctly when the vector log namespace is enabled. The only change required is related to the "global log schema". The vector namespace no longer uses the "global log schema", so sinks that use this to fetch data need to switch to getting this data from somewhere else. Usually either from "semantic meaning", or from vector metadata.

Global Log Schema Field	Migrate To
message	semantic meaning ("message")
host	semantic meaning ("host")
timestamp	semantic meaning ("timestamp"), defaulting to the current time if it doesn't exist and is appropriate
source_type	%vector.source_type should always exist for messages using the vector namespace

Since these sinks will rely on certain semantic meaning fields, it would useful to also have sink requirements which can enforce that the required meanings are set, and that they are the correct type. This involves creating a schema::Requirement object that just lists the semantic meaning name, the type, and whether it is required / optional, and adding it to the input in the SinkConfig::input function. These should be fairly straightforward to add to sinks.

Since sink requirements (at least initially) will only be required (for most sinks) when the Vector namespace is used, we should either check the LogNamespace when creating the requirements, or potentially only enable sink requirements with the Vector namespace.

For each sink:

1. Migrate all uses of the "Global Log Schema" (except for tests / default config options) to use helper methods that fetch data from either the "Global Log Schema" (Legacy namespace) or from semantic meaning / Vector metadata (Vector namespace).
2. Add sink requirements

Sinks

• Add log namespace support to aws_cloudwatch_logs sink #16482
• Add log namespace support to datadog_events sink #16484
• chore(datadog_logs sink): Add log namespace support to datadog_logs sink #15473
• Add Log Namespacing support to Elasticsearch sink #16502
• Add Log Namespace support to GCP sinks #16402
• Humio wraps splunk_hec_logs and only uses log_schema in config defaults
• Add Log Namespacing support to influxdb_logs sink #16539
• Add Log Namespacing to Kafka sink #16494
• Add Log Namespacing support to Loki sink #16454
• Add LogNamespace support to Sematext sinks #16435
• Add Log Namespacing support to Axiom sink #16493
• Add Log Namespacing to Azure Monitor Logs sink #16474
• Add Log Namespacing support to Datadog Archives sink  #16549
• Add Log Namespacing support to Honeycomb sink #16452
• Add Log Namespacing support to LogDNA #16457
• Add LogNamespace support to Papertrail sink #16430
• Add Log Namespace support to Pulsar sink #16450
• Add Log Namespace support to Databend sink #16585

Other Work

• Audit sources / transforms to ensure that semantic meaning for "global log schema" values are correct. These are message, host, timestamp (source_type is sometimes used, but can be fetched directly from vector metadata)
• Enable sink requirements automatically when the Vector namespace is enabled #16683
• Allow enabling sink requirements (schema.validation) without schema definitions (schema.enabled) #16534
• TransformConfig::outputs should accept a list of schema definitions #16730
• Set runtime schema definitions in the topology #16732
• Check that any sinks added after this list was created are covered