[SPARK-58204][SQL] Fix unprotected mutable state in RegExpReplace, RegExpExtractBase, StringTranslate, FormatNumber, and NamedLambdaVariable by marking them stateful

[vinodkc]

What changes were proposed in this pull request?

Override stateful: Boolean = true on five Catalyst expressions that maintain mutable
@transient state but were not marked stateful:

• RegExpReplace
• RegExpExtractBase (RegExpExtract, RegExpExtractAll)
• StringTranslate
• FormatNumber
• NamedLambdaVariable

For NamedLambdaVariable, also override withNewChildrenInternal to reset the AtomicReference on copy while preserving exprId. LeafLike.withNewChildrenInternal returns this by default, which would make freshCopyIfContainsStatefulExpression() a no-op even with the stateful flag set.

Why are the changes needed?

freshCopyIfContainsStatefulExpression() only copies subtrees containing a stateful = true node. Without the override, these expressions are shared across projections. When two projections evaluate concurrently — e.g. via ConvertToLocalRelation on the driver or pipelined execution on executors — threads race on the shared @transient cache fields and silently corrupt results.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Added one test per affected group in the existing suites (HigherOrderFunctionsSuite, RegexpExpressionsSuite, StringExpressionsSuite), each asserting stateful == true and that freshCopyIfContainsStatefulExpression() returns a distinct instance with independent state.

Was this patch authored or co-authored using generative AI tooling?

No