Clarify View name is not subject to instrument name syntax validation

[cijothomas]

The SDK spec is currently silent on whether the metric stream name provided via View stream configuration must conform to the instrument name syntax. Implementations have diverged on this: .NET and Rust validate the View-provided name against the instrument name syntax (and reject/drop the stream on mismatch), while Go, Java, Python, and C++ pass it through without validation.

This PR makes the spec explicit that View-provided names are not subject to instrument name syntax validation.

Discussion context: #5092 (comment) and follow-ups.

[dashpole]

I also checked (using AI, with references):

• Erlang: Doesn't validate the stream name. It validates instrument names, but doesn't enforce them (just logs).
• Kotlin: Doesn't implement views.
• PHP: Does not validate at instrument creation or view streams
• Swift: Does not validate at instrument creation or view streams.

[dashpole]

I think it is fine to use MUST NOT as long as the maintainers for .NET and Rust are on-board to change after this merges.

[cijothomas]

I think it is fine to use MUST NOT as long as the maintainers for .NET and Rust are on-board to change after this merges.

@martincostello Could you check if .NET is okay? (I am okay, and can send the PR with the fix to adjust to this, if this is merged)

[martincostello]

@cijothomas Sounds ok to me.

[lalitb]

LGTM. This matches current C++ SDK behavior: View-provided stream names are passed through without instrument-name syntax validation.

[cijothomas]

@jack-berg could you review?

[jack-berg]

PR to add a test to codify the opentelemetry-java behavior: open-telemetry/opentelemetry-java#8412

[cijothomas]

@carlosalberto Could you merge this in and include it part of release #5096 ?