Added ctx arguments to execute

[assembly-winston]

What kind of change does this PR introduce?

Added context.Context argument to each variant of the Execute() function, enabling users to pass context-based cancelation to the functions.

What is the current behavior?

There is no way to set deadlines/timeouts for operations to the DB.

What is the new behavior?

We allow the user to pass in a ctx to new variants of the Execute() function that are passed in to http.NewRequestWithContext() rather than the plain http.NewRequest, which defaults to context.Background(), which has no timeout.

Additional context

More info: https://go.dev/doc/database/cancel-operations

[assembly-winston]

Fixes issue 7 in supabase-go: supabase-community/supabase-go#7