update: reorganize imports, add URL rewriting support, and minor refactoring

- cmd/lerproxy/reverse/proxy.go
  - Reorganized imports for logical grouping.

- cmd/lerproxy/main.go
  - Added URL rewriting capability and updated command-line usage documentation.
  - Reorganized imports for consistency.
  - Replaced `context.T` with `context.Context` for standardization.
  - Updated timeout handling logic to use `context.WithTimeout`.

- pkg/protocol/ws/connection.go
  - Replaced `fmt.Errorf` with `errorf.E` for error formatting.

- cmd/lerproxy/util/util.go
  - Renamed file for better clarity.
  - Removed unnecessary package documentation.

- cmd/lerproxy/hsts/proxy.go
  - Removed redundant package comments.

- cmd/lerproxy/tcpkeepalive/listener.go
  - Removed redundant package comments.
  - Adjusted import order.

- cmd/lerproxy/buf/bufpool.go
  - Removed unnecessary package comments.

- cmd/lerproxy/README.md
  - Updated package usage examples and installation instructions.
  - Removed outdated and unnecessary instructions.

cmd/lerproxy/buf/bufpool.go

@@ -1,4 +1,3 @@
-// Package buf implements a simple concurrent safe buffer pool for raw bytes.
 package buf
 
 import "sync"