React UI: Starting Screen Progress Bar Should Start at 0

[LeviHarrison]

Not all WAL replays start at segment 0, so we must set the progress bar's zero value to the start point. As it turns out, the min prop of Bootstrap's progress bar doesn't seem to do anything, so this PR implements an alternative way of setting a minimum.

Fixes #8903

[juliusv]

From glancing at https://github.com/reactstrap/reactstrap/blob/master/src/Progress.js, it does use the min value, but only for ARIA attributes. So we probably still want to set it, even though it has no visual influence.

Btw. react-bootstrap also seems to take it into account properly for the displayed width (https://github.com/react-bootstrap/react-bootstrap/blob/c03150e24846d9df32bad7d0757a8be5848babbc/src/ProgressBar.tsx#L137), but we're using reacstrap in Prometheus (and not saying we should change that now :)).

[juliusv]

Other than that, 👍

[juliusv]

Thanks!