Replace static parameters in route pattern for telemetry

[tomerqodo]

Benchmark PR from qodo-benchmark#20

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Note

Improves route diagnostics/debug output by substituting required values into route patterns and refining constraint rendering.

• Add RoutePatternDebugStringFormatter to format RoutePattern debug strings by replacing parameters with matching RequiredValues, preserving literals, constraints, and leading slashes; returns / when empty
• Change RoutePattern.DebuggerToString() to use the new formatter; minor cleanup (remove LINQ and unused separator constant)
• Improve RoutePatternParameterPart.DebuggerToString() to prefer constraint.Content, render RegexRouteConstraint as regex(pattern), and fall back to policy type when needed
• Test Add comprehensive unit tests for formatter behaviors (substitutions, catch-alls, literals, constraints, leading slash) and update MVC EndpointMetadataProviderTest expected route to reflect substituted values

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[tomerqodo]

@cursor review