feat: generate nonce for HttpAgent calls

[krpeacock]

Description

HttpAgent will now provide a unique nonce in calls to ensure that the replica treats each call as unique.

How Has This Been Tested?

Tested in our integration test suie

Checklist:

• My changes follow the guidelines in CONTRIBUTING.md.
• The title of this PR complies with Conventional Commits.
• I have edited the CHANGELOG accordingly.
• I have made corresponding changes to the documentation.

[ericswanson-dfinity]

There is at least one place that is still calling <agent>.addTransform(makeNonceTransform()): https://github.com/dfinity/agent-js/blob/main/demos/ledgerhq/src/main.js#L86

and a few that add a different nonce transform, but without specifying the disableNonce option.
Examples:

• https://github.com/dfinity/agent-js/blob/main/packages/agent/src/agent/http/http.test.ts#L52
• https://github.com/dfinity/agent-js/blob/main/packages/agent/src/actor.test.ts#L102

[krpeacock]

There is at least one place that is still calling <agent>.addTransform(makeNonceTransform()): https://github.com/dfinity/agent-js/blob/main/demos/ledgerhq/src/main.js#L86

and a few that add a different nonce transform, but without specifying the disableNonce option. Examples:

• https://github.com/dfinity/agent-js/blob/main/packages/agent/src/agent/http/http.test.ts#L52
• https://github.com/dfinity/agent-js/blob/main/packages/agent/src/actor.test.ts#L102

Updated the changelog with upgrade instructions!