Generate per-partition service endpoint metadata

[ewbankkit]

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Add generated per-partition service endpoint metadata to the top-level endpoints package.
Required for migration of the Terraform AWS Provider's aws_service data source away from the AWS SDK for Go v1.

Relates #1176.

% go test ./...
?   	github.com/hashicorp/aws-sdk-go-base/v2/configtesting	[no test files]
?   	github.com/hashicorp/aws-sdk-go-base/v2/internal/awsconfig	[no test files]
?   	github.com/hashicorp/aws-sdk-go-base/v2/internal/constants	[no test files]
?   	github.com/hashicorp/aws-sdk-go-base/v2/internal/errs	[no test files]
?   	github.com/hashicorp/aws-sdk-go-base/v2/internal/generate/common	[no test files]
?   	github.com/hashicorp/aws-sdk-go-base/v2/internal/slices	[no test files]
?   	github.com/hashicorp/aws-sdk-go-base/v2/internal/test	[no test files]
?   	github.com/hashicorp/aws-sdk-go-base/v2/mockdata	[no test files]
?   	github.com/hashicorp/aws-sdk-go-base/v2/servicemocks	[no test files]
ok  	github.com/hashicorp/aws-sdk-go-base/v2	16.756s
ok  	github.com/hashicorp/aws-sdk-go-base/v2/diag	1.304s
ok  	github.com/hashicorp/aws-sdk-go-base/v2/endpoints	0.834s
ok  	github.com/hashicorp/aws-sdk-go-base/v2/internal/config	0.866s
ok  	github.com/hashicorp/aws-sdk-go-base/v2/internal/expand	0.649s
ok  	github.com/hashicorp/aws-sdk-go-base/v2/logging	1.466s
ok  	github.com/hashicorp/aws-sdk-go-base/v2/tfawserr	1.115s
ok  	github.com/hashicorp/aws-sdk-go-base/v2/useragent	1.469s
ok  	github.com/hashicorp/aws-sdk-go-base/v2/validation	1.578s

[jar-b]

LGTM 🚀