[featuregate] Validate arguments to Register

[mx-psi]

Description:

• Validate Gate IDs: ids must be alphanumeric with dots. At a minimum we have to disallow , to avoid ambiguity in the CLI, but I am being intentionally more restrictive here
• Validate URLs: we check that a valid URL can be built from it using the net/url stdlib package
• Validate versions: we check that a valid version is passed to the To/FromVersion options using hashicorp's libraries and also that the implicit version range, when defined, is not empty.

This does not change the public API types, it only adds validation.

Relates to #8220

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files	Coverage Δ
featuregate/gate.go	100.00% <100.00%> (ø)
featuregate/registry.go	100.00% <100.00%> (+4.59%)	⬆️

... and 3 files with indirect coverage changes

📢 Thoughts on this report? Let us know!

[mx-psi]

Can you take one (hopefully) final look @bogdandrutu ?

[bogdandrutu]

Would be good to have the same setup in core like https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/.gitattributes to not expand all the sum files.

[mx-psi]

Would be good to have the same setup in core like https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/.gitattributes to not expand all the sum files.

See #8810