util: render and parse names in the MoQT safe form

[afrind]

safeName() renders MoQT namespaces and track names in the form RECOMMENDED by moq-transport, "Representing Namespace and Track Names"; parseSafeBytes(), parseSafeNamespace() and parseSafeFullTrackName() invert it.

The encoding is injective, so callers that key on the result — metric labels, filenames, authorization schemes — cannot have two distinct names collapse onto one rendering, while names made of ordinary characters stay readable. Parsing splits a full name at the last "--", which stays unambiguous because an encoded track name never contains a hyphen.

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[gmarzot]

@gmarzot reviewed 5 files and all commit messages.
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[gmarzot]

mmmm ... "injective" but not "surjective"

"The encoding function $f$ is injective, which is logically equivalent to the existence of a left-inverse decoding function $g$ such that $g \circ f = \text{id}_X$. Reversibility is thus guaranteed over the image $f(X)$.While the mapping is left-invertible, it is not a bijection due to non-surjectivity over the codomain $Y$. Therefore, global two-sided invertibility is absent, as the decoder must handle an undefined or error state for arguments $\notin \text{Im}(f)$."

[afrind]

mmmm ... "injective" but not "surjective"

Ok clear evidence I did not write the commit summary

[gmarzot]

@gmarzot reviewed 1 file and all commit messages.
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