feat: add TL FIPS SIG image config and e2e

[mxj220]

What this PR does / why we need it:
Adds SIG image config and E2E for TrustedLaunch FIPS 22.04 VHD
Which issue(s) this PR fixes:

Fixes #

[Copilot]

Pull request overview

Adds support for a new Ubuntu 22.04 Gen2 FIPS + TrustedLaunch SIG image definition across the AgentBaker datamodel and e2e suite, enabling validation that this VHD can bootstrap successfully.

Changes:

• Introduces a new Distro constant for Ubuntu 22.04 Gen2 FIPS TrustedLaunch and adds it to the “available on VHD” lists.
• Adds a new Ubuntu SIG image config template + mapping entry for the new distro, updating SIG config unit expectations accordingly.
• Adds an e2e VHD config entry and a new scenario test that enables Trusted Launch + FIPS 140-3 encryption capability.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
pkg/agent/datamodel/types.go	Adds new distro constant and includes it in AKSDistrosAvailableOnVHD.
pkg/agent/datamodel/sig_config.go	Registers the new distro in Ubuntu/containerd/gen2 distro lists and adds a SIG image definition template + mapping entry.
pkg/agent/datamodel/sig_config_test.go	Extends expected maintained SIG config map and updates expected Ubuntu SIG config count.
e2e/config/vhd.go	Adds a new e2e Image entry for the Ubuntu 2204 Gen2 FIPS TL SIG image.
e2e/scenario_test.go	Adds an e2e scenario validating bootstrap for the new TL+FIPS 2204 Gen2 VHD.