fix: evaluates subdomains correctly when determining known hosts

[krpeacock]

Description

With the recent change to the default host in 0.19.1, the parsing logic was incorrectly not handling subdomains or ports correctly when determining whether the agent should use the current location as a host.

This led to applications using a default asset canister configuration to make calls to icp-api.io, which is currently not configured under the content security policy in ic-assets.json.

These changes improve the logic and correctly use the host on local and network deployment when no host is specified.

How Has This Been Tested?

New unit test cases. Also, was manually tested by installing a build to a fresh dfx new project and deploying locally and to mainnet.

Live site: https://rqqdj-jqaaa-aaaab-qaiha-cai.icp0.io/

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.

[github-actions]

size-limit report 📦

Path	Size
@dfinity/agent	87.03 KB (+0.05% 🔺)
@dfinity/candid	13.52 KB (0%)
@dfinity/principal	5.15 KB (0%)
@dfinity/auth-client	92.54 KB (0%)
@dfinity/assets	89.56 KB (0%)
@dfinity/identity	89.81 KB (0%)
@dfinity/identity-secp256k1	232.13 KB (+0.03% 🔺)