adds WebSettings to allow controlling maximumAge of location update

[josh-burton]

HTML geolocation supports a maximumAge parameter, which controls whether a cached location value can be returned.

By default this is set to zero, meaning no cached values are allowed and location updates can take some time.

This PR introduces a WebSettings class to allow customising settings on the web.

This PR also modifies the getCurrentPosition to accept a locationSettings parameter. The existing parameters are deprecated to avoid a breaking change.

List at least one fixed issue.

Pre-launch Checklist

• I made sure the project builds.
• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is does not need version changes.
• I updated CHANGELOG.md to add a description of the change.
• I updated/added relevant documentation (doc comments with ///).
• I rebased onto main.
• I added new tests to check the change I am making, or this PR does not need tests.
• I made sure all existing and new tests are passing.
• I ran dart format . and committed any changes.
• I ran flutter analyze and fixed any errors.