Don't generate a SDK for runtime-versioner patching (#3540)

This PR removes the requirement of generating a SDK in order to patch
smithy-rs runtime crates into an already released SDK version for
testing. This is possible now that all the runtime crates are
independently versioned. The tool also takes multiple paths as input for
the runtime crate locations. This makes it possible to pass in the
`rust-runtime` and `aws/rust-runtime` directories from smithy-rs (done
by default by one of the subcommands).

Some of the publisher tool's package resolution code is moved into
smithy-rs-tool-common so it can be better shared across the tools, and
as part of this, the version in the package handle was made optional.

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