Prepare Web 3.3.0 with license enforcement

[JimBobSquarePants]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following matches the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
• I have provided test coverage for my change (where applicable)

Description

Prepare ImageSharp.Web, AWS, and Azure provider releases 3.3.0 on release/3.3.x, based on release/3.2.x.

• Update SharedInfrastructure from release/3.1.x for Licensing 1.0.3, repository guidance, and the security policy.
• Update ImageSharp to 3.2.0 and set all three minimum release versions to 3.3.
• Suppress the five corrected ImageSharp advisories while the database updates are pending, with a removal note.
• Run .NET 6 CI on Ubuntu 22.04, Windows 2022, and Intel macOS. Remove .NET 7 runs.
• Build PRs and publish alpha packages on release-branch pushes.