request-rewrite: silent no-op for invalid path rewrite config and query reordering on path-only rewrite

Summary

request-rewrite has three confirmed behavior issues that can hide configuration problems and change request semantics.

1) Invalid path regex is treated as silent no-op instead of config error

• Example config:

pathRewrite:
  type: ReplaceRegexMatch
  replaceRegexMatch:
    pattern: "["
    substitution: "/x"

• Actual: returns UpstreamRequestModifications with no rewrite (warn log only).
• Expected: fail closed with a configuration error response.
• Evidence:
  • Test: requestrewrite_test.go:1169
  • Behavior: requestrewrite.go:360-364

2) Unsupported pathRewrite.type is silently ignored

• Example config:

pathRewrite:
  type: TypoRewriteType
  replaceFullPath: /x

• Actual: warn + no-op, no failure response.
• Expected: fail closed with a configuration error response.
• Evidence:
  • Test: requestrewrite_test.go:1194
  • Behavior: requestrewrite.go:367-369

3) Path-only rewrites reorder query parameters

• Example input:
  • Request path: /v1/orders/42?b=2&a=1
  • Rewrite: ReplaceFullPath to /new
• Actual output: /v1/new?a=1&b=2 (query order changed)
• Expected: preserve original query order for path-only rewrites.
• Evidence:
  • Test: requestrewrite_test.go:1145
  • Cause: requestrewrite.go:467 (url.Values.Encode() canonicalization)

Start with requestrewrite.go at lines 360-369 and 467, then read the related cases in requestrewrite_test.go at lines 1145, 1169, and 1194. Confirm the existing behavior and update the tests so invalid regexes and unsupported types produce configuration errors while path-only rewrites preserve query order; done means all request-rewrite tests pass.