Render the git graph on the server (#12333)

Rendering the git graph on the server means that we can properly track flows and switch from the Canvas implementation to a SVG implementation.

* This implementation provides a 16 limited color selection
* The uniqued color numbers are also provided
* And there is also a monochrome version
*In addition is a hover highlight that allows users to highlight commits on the same flow.

Closes #12209

Signed-off-by: Andrew Thornton art27@cantab.net
Co-authored-by: silverwind <me@silverwind.io>

public/img/svg/material-invert-colors.svg

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+<svg viewBox="0 0 768 768" class="svg material-invert-colors" width="16" height="16" aria-hidden="true"><path d="M384 627V163.5l-135 135c-36 36-57 85.5-57 136.5 0 103.19 88.8 192 192 192zm181.5-373.5C666 354 666 514.5 565.5 615 516 664.5 450 690 384 690s-132-25.5-181.5-75C102 514.5 102 354 202.5 253.5L384 72z"/></svg>

public/img/svg/material-palette.svg

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+<svg viewBox="0 0 768 768" class="svg material-palette" width="16" height="16" aria-hidden="true"><path d="M559.5 384c27 0 48-21 48-48s-21-48-48-48-48 21-48 48 21 48 48 48zm-96-127.5c27 0 48-21 48-48s-21-48-48-48-48 21-48 48 21 48 48 48zm-159 0c27 0 48-21 48-48s-21-48-48-48-48 21-48 48 21 48 48 48zm-96 127.5c27 0 48-21 48-48s-21-48-48-48-48 21-48 48 21 48 48 48zM384 96c159 0 288 115.5 288 256.5 0 88.5-72 159-160.5 159H456c-27 0-48 21-48 48 0 12 4.5 22.5 12 31.5s12 21 12 33c0 27-21 48-48 48-159 0-288-129-288-288S225 96 384 96z"/></svg>