Add UseLegacyAttributes flag to telemetry config

[ChrisJBurns]

Summary

• Adds a new UseLegacyAttributes boolean field to the telemetry Config struct, defaulting to true for backward compatibility with existing dashboards and alerts
• Plumbs the flag through CLI (--otel-use-legacy-attributes), config file (use-legacy-attributes), operator CRD types (OpenTelemetryConfig.useLegacyAttributes), operator spectoconfig (reads from CR spec), runner config builder
• CRDs updated: VirtualMCPServer, MCPServer, MCPRemoteProxy — all include useLegacyAttributes with default: true
• The flag is not yet consumed by the telemetry middleware; a follow-up PR will add the conditional attribute emission logic

Context

This is the first PR in a series to support the MCP OTEL semantic conventions migration. The flag provides the plumbing so that a subsequent PR can conditionally emit legacy attribute names alongside the new standard names. The default will change to false in a future release, and the flag will eventually be removed.

Test plan

• Unit tests for getTelemetryFromFlags updated to cover UseLegacyAttributes plumbing (CLI precedence, config fallback, default behavior)
• Runner config builder tests updated with new parameter
• Spectoconfig tests updated with UseLegacyAttributes assertion and new test case for reading from CR spec
• CRD manifests regenerated for VirtualMCPServer, MCPServer, and MCPRemoteProxy
• go build ./... compiles cleanly
• task lint passes with 0 issues
• All affected package tests pass

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.35%. Comparing base (468c29f) to head (e76e459).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3729   +/-   ##
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  Coverage   66.35%   66.35%           
=======================================
  Files         427      427           
  Lines       41794    41800    +6     
=======================================
+ Hits        27731    27737    +6     
  Misses      11953    11953           
  Partials     2110     2110           

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