Update mockery to v3 and golangci-lint to v2

[Chengxuan]

Both tools needed major version bumps.

• golangci-lint was pinned at v1.64.8, the last v1 release (the project has fully moved to v2, which uses a new config schema).
• mockery was installed from github.com/vektra/mockery/cmd/mockery@latest, an unversioned v1 import path that's frozen years behind current releases. Neither had a version left to bump within their existing major, so this does both migrations together.

They're bundled in one PR because the mockery jump is what makes the golangci-lint jump safe to verify: golangci-lint v2's staticcheck (merged with gosimple/stylecheck) flags a few things in the mock output as generated code changes shape, and running the full make lint && make test cycle once, on the final state of both tools, is the only way to be confident neither upgrade silently broke the other's assumptions. Splitting them would mean landing a golangci-lint config rewrite that's only really been exercised against soon-to-be-replaced mocks, or landing a mock rewrite that hasn't been linted with the tool version it'll actually ship next to.

Changes

• .golangci.yml: migrated to the v2 config schema (via golangci-lint migrate), same linter set preserved (v2 merges gosimple/stylecheck into staticcheck; errcheck/govet/ineffassign/unused are default-enabled in v2 and no longer need listing).
• .mockery.yml (new): v3 is config-driven, no CLI flags. Configured the same 4 interfaces (Backend, Subscription, Manager, BlockListener) at their existing output paths and package names, with unroll-variadic: true to preserve v2's variadic-arg-flattening behavior (v3 defaults to passing them as a single slice, which broke two existing test suites' .On(...) expectations).
• Makefile: mocks target now just runs mockery (config does the rest); lint/mockery install targets bumped to v2.13.2 / v3.8.0.
• 4 mock files regenerated — same struct/constructor names, additive EXPECT() API, no test changes needed.
• Fixed the new issues golangci-lint v2 caught:
  • 6 staticcheck (QF1008): redundant embedded-field selectors (bl.BlockListenerConfig.X → bl.X) in exec_query.go, prepare_transaction.go, blocklistener.go, confirmation_reconciler.go, ethrpc.go.
  • 9 goconst: repeated JSON map-key string literals in pkg/ethrpc replaced with shared constants (keyAddress, keyBlockHash, keyBlockNumber, keyHash, keyLogsBloom, keyNumber, keyTransactionIndex).

Test plan

• make lint — 0 issues
• make test — all packages pass
• Verified mock regeneration is deterministic (mockery run twice produces identical output)
• Verified make mocks works from a clean toolchain (binaries removed and reinstalled)

🤖 Generated with Claude Code and then edited to make the wordings clear

[Chengxuan]

Hold on for this upgrade as it will change developer toolings and affect the wider firefly ecosystem