Uint8Array to Ascii. Similar to btoa, but safer.

Internally, this first attempts to call Uint8Array.prototype.toBase64, if it is available in the runtime (caniuse).

Due to our minimum deno version being 2.3.1 (Alpine 3.23.3 Stable), which doesn't implement it (was added in 2.5), we need to fallback if needed. If it isn't installed, we fallback to, if btoa and TextDecoder are both available, trying to use btoa on the result of TextDecoder.prototype.decode.

Should TextDecoder be unavailable or error (likely for some binary data), we attempt to call btoa with our own text decoder based on String.fromCharCode. This too can fail on some binary outputs.

Should this too fail, or should btoa not be available, we use this implementation from stackoverflow, exposed as rawUtoa.