feat(storage): list API to accept both prefix and path

[Samaritan1011001]

Description of changes

List API will now accept either prefix or path as input. Depending on which is given, their respective types are suggested in the IDE and output has key or path respectively.
Some notes,

• If prefix is given, options show the accessLevel, targetIdentityId (this is as is currently in V6)
• if no input object is given or its empty, default guest prefix is assumed (this is as is currently in V6).
• If path is given, options does not show accessLevel, targetIdentityId (gen2 feature)

Below table shows the different type changes in index.ts.

Note: None of the exposed type names have changed. Only the first two rows are the ones exposed via aws-amplify/storage.

file	feature branch(gen2-storage)	PR change
src/index.ts	ListAllInput, ListPaginateInput, ListAllOutput, ListPaginateOutput	No change
src/providers/s3/index.ts	ListAllInput, ListPaginateInput, ListAllOutput, ListPaginateOutput	No change
src/types/index.ts	StorageListInput	StorageListInputPrefix, StorageListInputPath
(options) src/providers/s3/types/index.ts	ListAllOptions, ListPaginateOptions	ListAllOptionsPrefix, ListPaginateOptionsPrefix, ListAllOptionsPath, ListPaginateOptionsPath
(inputs) src/providers/s3/types/index.ts	ListAllInput, ListPaginateInput	ListAllInput, ListPaginateInput, ListAllInputPath, ListPaginateInputPath, ListAllInputPrefix,ListPaginateInputPrefix
(outputs) src/providers/s3/types/index.ts	ListOutputItem, ListAllOutput, ListPaginateOutput	ListOutputItemKey, ListOutputItemPath ListAllOutput, ListPaginateOutput ListAllOutputPrefix, ListAllOutputPath ListPaginateOutputPath, ListPaginateOutputPrefix

Issue #, if available

Description of how you validated changes

Linked to a sample app and could complete the list operation both ways

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jimblanc]

LGTM one small nit