[Web][A11y] Fix link onClick behavior on links

[johnsonmh]

Right now, when semantics are enabled in flutter web, anchor tags are created around anything that is Semantics(link: true). These anchor tags have an href="#". Right now, when these anchor tags are clicked, they actually navigate the page to /#, and then the underlying flutter onTap is also triggered. We don't want the anchor tag to actually trigger a redirect, since the onTap is handled by the framework. We can avoid this by calling preventDefault() on the anchor tag's click events.

Internal bug: b/321779318

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Changes reported for pull request #49984 at sha ce9d21ad71aba4496e23efecac4d2b748a54d280

[mdebbar]

Sorry for the late reply here, I didn't know about this PR.

I've been working on fixing multiple issues in links (Link PR and engine PR). Both PRs are still WIP. The issue you are addressing here should also be fixed by the PRs once they are complete.

[christopherfujino]

@mdebbar what's the latest? is this PR still relevant?