fix: add /v2 module path for Go v2 compatibility

[mrhinton101]

###Description

This change updates the module path and internal imports to make the pango module compatible with Go’s semantic import versioning for v2.x.

Changes include:
• Updating the go.mod path to module github.com/PaloAltoNetworks/pango/v2
• Updating all internal import paths to include the /v2 suffix
• Updating and verifying the example/main.go file to reflect the new module structure

###Motivation and Context

Go module tooling requires that any version v2.0.0 or later include a /v2 suffix in both the go.mod declaration and all import paths. Without this, consumers of the module encounter errors like:

go: github.com/PaloAltoNetworks/pango@v2.0.0-rc6: invalid version: module contains a go.mod file with the wrong module path

This update allows proper use of go get github.com/PaloAltoNetworks/pango/v2@v2.0.0-rc6 and other v2+ versions.

###How Has This Been Tested?
• Verified the build with go build ./... — no new build errors introduced; all errors match those present on the main branch
• Verified tests with go test ./... — confirmed no additional test failures introduced
• Verified example/main.go builds and runs correctly when imported using the updated /v2 path and a local module replace directive

Environment: go1.23.1 darwin/arm64

###Screenshots (if appropriate)

N/A

###Types of changes
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

###Checklist
• I have updated the documentation accordingly.
Yes – updated and verified example/main.go usage example.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes if appropriate.
N/A – no functional logic changes.
• All new and existing tests passed.
No new test failures introduced; build errors present on main persist unchanged.

[mrhinton101]

Ready for Review