Update anchor tags and enhance navigation cues for screen readers

[WilliamHolden]

This pull request does two things. The first is that it changes any non link anchor tags to use href="javascript:void(0)" instead of href="#".

Both of these href attributes are trying to achieve the same thing so we should only use one for consistency reasons. There are a few reasons to prefer href="javascript:void(0)" over href="#".

1. href="#" changes the actual URL leading to unwanted effects like the page scrolling to the top
2. href="#" causes backbone to call an internal checkURL() function which leads to unwanted effects like the issue below:
   #7893
3. href="#" doesn't work well with screen readers (this can be mitigated by adding role="button")

There are other reasons as well. See the top answer on https://stackoverflow.com/questions/134845/which-href-value-should-i-use-for-javascript-links-or-javascriptvoid0

Ideally, a lint rule will be added to enforce this change in the future but I could not find a good eslint plugin. The closest one I found was "jsx-a11y/href-no-hash" but I think this rule was created for jsx specifically

The next thing this pull request does is make some enhancements to the navigational cues for screen readers through the use of aria-labels, tabindex, and role attributes. There is still some work to be done here and I will make another pull request with more navigational cue updates.

[WilliamHolden]

I have another WIP branch which depends on some of the changes in this PR. When this PR passes review and gets merged I will make the PR for the WIP branch into galaxy dev (when it's not WIP anymore of course). For now I have set up a temporary PR in my own repo to keep track of the changes: WilliamHolden#1.

[martenson]

Thanks @WilliamHolden !