Update trait impls and conversions for byte types

[Rigidity]

This PR adds missing conversions for Bytes, BytesImpl, and Program, and removes PartialEq implementations for other types to reduce complexity.

It also changes From to TryFrom in some cases where the conversion is fallible:

Note: This trait must not fail. The From trait is intended for perfect conversions. If the conversion can fail or is not perfect, use TryFrom.

https://doc.rust-lang.org/std/convert/trait.From.html

[coveralls-official]

Pull Request Test Coverage Report for Build 7626926267

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• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.4%) to 84.684%

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Totals
Change from base Build 7547611610:	-0.4%
Covered Lines:	11091
Relevant Lines:	13097

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💛 - Coveralls

[arvidn]

looks good, just a few comments and questions