[KYUUBI #7727][UTIL] Trim each side of the pair in genKeyValuePair

[LuciferYang]

Why are the changes needed?

Closes #7727.

genKeyValuePair trimmed only the concatenated string (s"$key=$value".trim), so whitespace between the key and value survived: genKeyValuePair("abc ", "123") returned "abc =123". redactConfValues splits an assembled argument on the first = and matches the key against an exact key set, so a spaced key ("<key> =") misses the set and the value is not redacted.

This matters for the Data Agent engine's API key. kyuubi.engine.data.agent.openai.api.key is not matched by the default pattern-based redaction, so exact-key redaction is its only guard, and session conf keys are not trimmed on the way to the engine command. A key carrying a trailing space slipped both stages and logged the API key value. Trimming each side (s"${key.trim}=${value.trim}") makes the assembled pair carry no inner whitespace, so the exact-key stage sees the clean key. Utils.redactCommandLineArgs also assembles through genKeyValuePair, so the same fix closes the hole at both assembly points.

How was this patch tested?

Added CommandUtilsSuite cases: symmetric-trim assertions (genKeyValuePair("abc ", " 123") -> "abc=123", including a tab) and a redaction round-trip that assembles a spaced Data Agent api-key argument and asserts redactConfValues masks it. Both fail on the old .trim.

build/mvn test -pl kyuubi-util-scala -am
build/mvn scalastyle:check spotless:check -pl kyuubi-util-scala -am
build/mvn test -pl kyuubi-common -am -DwildcardSuites=org.apache.kyuubi.UtilsSuite

kyuubi-util-scala green on Zulu 17.0.18 (22/22), scalastyle 0 errors, spotless clean; kyuubi-common UtilsSuite (which exercises redactCommandLineArgs) 14/14.

Was this patch assisted by generative AI tooling?

Assisted-by: Claude Opus 4.8