Add HEAD method support to Ping middleware

[umputun]

Ping middleware now handles both GET and HEAD methods for the /ping endpoint. HEAD returns 200 OK with headers but no body, which is useful for lightweight health checks by monitoring tools.

Changes:

• Ping middleware accepts HEAD in addition to GET
• HEAD returns status and headers only (no "pong" body)
• Refactored tests to use subtests covering GET, HEAD, POST, and other paths

Also includes:

• Dependency updates (golang.org/x/crypto, golang.org/x/sys)
• Modernize linter fixes: interface{} → any, max() builtin, strings.SplitSeq

[coveralls]

Pull Request Test Coverage Report for Build 20806401957

Details

• 10 of 10 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 88.172%

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Totals
Change from base Build 20444828212:	0.2%
Covered Lines:	738
Relevant Lines:	837

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💛 - Coveralls

[Copilot]

Pull request overview

This pull request adds HEAD method support to the Ping middleware for lightweight health checks and includes dependency updates and linter-driven modernization fixes.

Key changes:

• Ping middleware now accepts HEAD requests in addition to GET, returning status and headers without a body
• Modernization: replaced interface{} with any alias throughout the codebase
• Applied modern Go idioms: max() builtin and strings.SplitSeq iterator pattern

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
middleware.go	Added HEAD method support to Ping middleware with proper documentation
middleware_test.go	Refactored tests into subtests covering GET, HEAD, POST, and other paths
rest.go	Replaced interface{} with any in function signatures
logger/logger.go	Replaced interface{} with any in Backend interface and implementation
gzip.go	Replaced interface{} with any in sync.Pool definition
benchmarks.go	Modernized interval calculation using max() builtin
realip/real.go	Attempted to use strings.SplitSeq for iteration
go.mod	Updated golang.org/x/crypto from v0.45.0 to v0.46.0 and golang.org/x/sys from v0.38.0 to v0.39.0
go.sum	Updated checksums for dependency updates
.golangci.yml	Added modernize and testifylint linters

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[Copilot]

The function strings.SplitSeq does not exist in the Go standard library. The standard function is strings.Split which returns a slice of strings. If you intended to use an iterator-based approach available in Go 1.23+, you would need strings.Fields or similar, but strings.SplitSeq is not a valid function name. This change will cause a compilation error.

Suggested change

	for addr := range strings.SplitSeq(xff, ",") {
	for _, addr := range strings.Split(xff, ",") {