Introduce StableHashMap to support hashable-1.5.0.0

[larskuhtz]

In hashable-1.4.5.0 the hash algorithm for types that are based on ByteArray changes from a custom version of fnv1 to xxhash. This changes the order of items in HashMaps, some of which are relevant for on-chain semantics.

Ideally, no use of unordered-containers should depend on the order of items, which is an internal detail of the data structure as indicated by the use of the term "unordered" in the name of the package. Unfortunately, Pact violates this assumption in a few places where the order of items affects on-chain semantics. In particular, the order in which modules are resolved and loaded is affected by this.

As work around, this PR introduces a StableHashMap that is backed by the class StableHashable. Instances of StableHashable promise to never change the hash value for a given value.

This PR also includes instances of StableHashable for a few basic types that are compatible with the hash values from hashable-1.4.4.0.

PR checklist:

• Test coverage for the proposed changes
• PR description contains example output from repl interaction or a snippet from unit test output

Additionally, please justify why you should or should not do the following:

• Confirm replay/back compat
• Benchmark regressions
• (For Kadena engineers) Run integration-tests against a Chainweb built with this version of Pact