chore(log): sync remaining log package files with upstream go-ethereum #2876

Background

#2837 already made log/handler.go byte-identical to go-ethereum's log/handler.go at 409aaefac. The remaining files under log/ still carry pre-existing divergence from upstream on dev-upgrade. This ticket tracks porting them.

Divergence inventory (baseline: go-ethereum 409aaefac)

• log/handler_glog.go — upstream rewrote it entirely: glogConfig + atomic.Pointer[glogConfig] + a sync.Map callsite cache, plus a glogWithAttrs wrapper type so child loggers follow later Verbosity/Vmodule changes on the parent. Our tree still has the old RWMutex + siteCache design, but already uses strings.SplitSeq (a newer idiom), so its lineage differs from 409aaefac. When porting, diff against the latest geth master, not only 409aaefac.
• log/logger_test.go — upstream adds TestLoggingWithVmoduleDowngrade and TestWithAttrsVerbosityChange, plus a small out → out.String() fix in TestJSONHandler.
• log/format.go — upstream renames reflect.Ptr → reflect.Pointer in FormatSlogValue's recover path.
• log/root.go — our tree has a local Enabled(level slog.Level) bool helper that upstream does not have; decide whether to keep it or align.

Approach

Same method as #2837: port file by file, verify with a byte-level diff against the matching upstream file, ship as an independent PR, and keep go test -count=1 ./log/... plus make all green.

Ref: #2837