Prepare klog release for Kubernetes v1.25 (Take 1)

What's Changed

• logcheck: contextual logging + enhanced checks by @pohly in #297
• hack/tools: drop dependency on golangci-lint by @pohly in #313
• StopFlushDaemon: document flushing on shutdown by @pohly in #314
• logcheck: fix detection of invalid * regexp in filter by @pohly in #315
• README.md: clarify -logtostderr by @pohly in #319
• Trim duplicates by @pohly in #324
• replace KObjs with KObjSlice by @pohly in #322
• support logr.Marshaler by @pohly in #325
• internal: remove unused TrimDuplicates by @pohly in #326
• save and restore state by @pohly in #320
• GitHub: use apidiff with more recent Go by @pohly in #329
• remove hack/tools by @pohly in #330
• GIT-331: fix shadowing key from the kv pair by @harshanarayana in #332
• klog.Fatal backtrace revert by @pohly in #328
• ktesting: capture log data in memory by @pohly in #327
• GIT-275: add tests for int and struct keys by @harshanarayana in #333

New Contributors

• @harshanarayana made their first contribution in #332

Full Changelog: v2.60.1...v2.70.0