Re-implement Bottlerocket template system for Out-of-tree Builds

[cbgbt]

Related to #2669

What I'd Like:
We need to be able to express settings dependencies for templates as described by the design document in #2834. This would allow the settings system to determine what settings and at what versions the API should render templates.

As an example, a template might look something like this:

[required-extensions]
motd = { version = "v1', helpers = ["boldface"] }
+++
Today's motd is {{ settings.motd }}

Let's pretend that the `motd` extension gives us a custom helper for boldfacing text {{ boldface "like this" }}.

Where the settings required are specified in a header called "frontmatter" and the template body is given as a string below.

To do:

• Implement template parser (schnauzer: implement v2 template parser #3284)
• Implement template renderer (schnauzer: Implement v2 template renderer #3302)
• Implement settings generator binary (Migrate to schnauzer v2 for generated settings #3316)
• Migrate thar-be-settings and existing config templates to the new renderer library (Migrate to schnauzer v2 for configuration file templates #3346)
• Migrate sundog and settings-generators to the new binary (Migrate to schnauzer v2 for generated settings #3316)
• Replace ReplaceTemplateMigration
• Write a migration guide to help users port existing templates (schnauzer: add v1->v2 template guide, resolve migration bugs #3488)