Fix SVG image performance & scaling

[BenHenning]

The fix in #4027 introduces DP-based scaling for images, and fixes some alignment/sizing issues. Unfortunately, these exposes a few problems:

1. Sometimes upscaling SVGs on Android seems to result in a blurry image (which suggests rasterization happening under the surface). Since we use AndroidX for SVG rendering internally, it seems likely that this is happening (though I didn't confirm). Trying different scaling techniques didn't work, but I suspect that changing the Picture's dimensions during creation time in AndroidSVG to something large (e.g. by adding a configurable scalar that we can set from Oppia Android) might ensure the rasterization is correct. Note that blurry images will also be a problem for bitmaps since there's no upscaling going on, so we need to add that, too.
2. SVG rendering generally seems slow, and using bitmaps (like we do for KitKat & Lollipop) doesn't actually fully fix the problem since it recomputes the bitmap on rebinding, and upscaling results in very large bitmaps that use up far too much app memory.

We want both upscaling and performant rendering for SVGs. I think that involves:

1. Computing the smallest size necessary to render the image without it resulting in blurriness (which probably requires better understanding all the different scenarios an SVG can be rendered)
2. Precomputing the bitmap and caching it via Glide (similar to what we do for LaTeX in Fix part of #4044: Add KotliTeX integration (direct LaTeX rendering) #4068) which should significantly improve performance. We do, however, need to make sure that any dependencies on display density are reflected in the caching message digest since the user changing the system's display zoom should result in recomputing the images (to ensure they don't waste space and/or end up blurry due to upscaling).

[BenHenning]

For searching context, this issue was found in 0.7-alpha (MR4).