feat(expr): support int8send and int8recv

[xiangjinwu]

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What's changed and what's your intention?

Only supports int8 right now. After ToBinary and FromBinary refactor, all types can be supported.

int8recv is not callable in PostgreSQL, but can be useful to decode a bytea into a bigint. Resolves #13069

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)

Release note

These functions are relatively stable in PostgreSQL, but still unsure whether they should be documented given its naming.

[codecov]

Codecov Report

Merging #13077 (d156d06) into main (4a8b0cb) will decrease coverage by 0.07%.
Report is 1 commits behind head on main.
The diff coverage is 47.82%.

@@            Coverage Diff             @@
##             main   #13077      +/-   ##
==========================================
- Coverage   68.27%   68.21%   -0.07%     
==========================================
  Files        1501     1501              
  Lines      252750   252773      +23     
==========================================
- Hits       172576   172422     -154     
- Misses      80174    80351     +177     

Flag	Coverage Δ
rust	68.21% <47.82%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/frontend/src/expr/pure.rs	87.69% <ø> (ø)
src/frontend/src/binder/expr/function.rs	78.51% <84.61%> (+0.06%)	⬆️
src/expr/impl/src/scalar/cast.rs	84.62% <0.00%> (-1.53%)	⬇️

... and 18 files with indirect coverage changes

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[lmatz]

LGTM, thanks