optimization: don't store bytestring length when it is statically known

[charles-cooper]

Simple Summary

The runtime format of a bytestring is like

<len 32 bytes> | < bytestring data>

Don't store the length in memory at runtime if length is statically known, as is known for constants and maybe some other cases.

Motivation

We can improve codesize and memory usage if we don't store the length at runtime if it's statically known. Also this will allow us to store constant bytestrings in the upcoming data section just like immutables (cf #2466).

Backwards Compatibility

Not a user-facing change. Could affect tracers but I am not aware of any tools that trace bytestring constants.

Dependencies

#2466

References

Copyright

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