Add executable artifacts with shared-scripts install scheme

[timkpaine]

Support shipping Rust binaries (bin/example targets) in wheels, in addition to the existing cdylib extension modules.

• New "shared-scripts" install scheme places an artifact in the wheel's .data/scripts/ directory so pip install puts it on PATH (the executable equivalent of shared-data).
• Executable artifacts (cargo-target-kind bin/example) are now copied: previously they fell through to the cdylib path and failed looking for a lib shared library.
• Skip the implicit --crate-type cdylib rustc arg for executables, which would otherwise build a binary target as a library.
• Add an executable_name() helper and a {executable} destination token.
• Route both compiled and generated outputs through shared-scripts, and forward shared_scripts from the build plan to hatchling build_data.

[codecov]

Codecov Report

❌ Patch coverage is 82.41758% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.40%. Comparing base (8345819) to head (1ac949f).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
hatch_rs/structs.py	78.84%	11 Missing ⚠️
hatch_rs/plugin.py	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #62      +/-   ##
==========================================
+ Coverage   81.01%   81.40%   +0.38%     
==========================================
  Files          10       10              
  Lines        1354     1441      +87     
==========================================
+ Hits         1097     1173      +76     
- Misses        257      268      +11     

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