Fixed CI linter failures blocking the configuration refactoring PR.

Changes

• goconst: Introduced constant.LocalhostAnyPort to deduplicate 27 instances of "localhost:0" across 11 files
• prealloc: Added capacity hints to slice allocations in meters.go, async_client_impl_test.go, set.go, and coordinator_e2e_test.go
• revive: Excluded common/{hash,io,time} packages from var-naming checks to suppress false positives on intentional standard library name reuse

// Before: scattered literals
server := NewServer("localhost:0")
client := Dial("localhost:0")

// After: centralized constant
server := NewServer(constant.LocalhostAnyPort)
client := Dial(constant.LocalhostAnyPort)

All linters now pass with 0 issues.

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