feat: add gcp home provider

[shreyassanthu77]

• used aws and cloudflare as a reference to implement this
• uses gcp project id as the bucket name cuz it's already globally unique and puts it in gcs (project region)
• uses google secrets manager to save secrets

few considerations

• secrets manager is not free and needs to be enabled manually (super cheap but still) should i do it more like cloudflare and put it in the bucket?
• the gcp error message extraction was kind of annoying, feels really hacky but big pickle said it's the only good way :)
• also added couple fixme comments for stuff i wasn't sure about what to do
• looks like it's everything is working fine

I will try to port a few my clients' pulumi automation setups to sst and try moving the common patterns to cloud build, cloud run, astro components and stuff if it works out well