Revisit 1024 char limit on label values

[carsonip]

There is a 1024 character (as in unicode characters) limit on string label values, on otlp (see code) and intakev2, because we used to depend on Beats & Fleet to set up mappings which would both set ignore_above: 1024 on keyword fields. As apm-server has migrated to ES apm-data plugin, revisit this limitation on label value.

#14716 is a related issue to handle an inconsistency in enforcing this limit.

[inge4pres]

AFAIR OpenTelemetry is also enforcing some limits on the Attributes key/value length?
Is it true? If yes, how do we discern the APM format, if we'd need to?

[carsonip]

AFAIR OpenTelemetry is also enforcing some limits on the Attributes key/value length?

There is truncation for OTel attributes but default truncation length is unlimited by default: https://opentelemetry.io/docs/specs/otel/common/#attribute-limits