Add support for binary non-XDR format

[traversc]

References to issues or other PRs

N/A

Describe the proposed changes

• Add native binary read/write support alongside existing XDR and ASCII support.
• Update tests to cover native-binary parsing and writing paths.
• Minor bug fix: on big-endian systems, XDR parser would try to write to a read-only buffer to fill NAs (gets implicitly copied/writable on little endian systems)

Additional information

Round trip example

obj <- list(
  data.frame(id = c(1L, 2L), value = c("a", "b")),
  "hello"
)
con <- file("native_in.rds", "wb")
serialize(obj, con, ascii = FALSE, xdr = FALSE, version = 3)
close(con)

import rdata

py_obj = rdata.read_rds("native_in.rds")
rdata.write_rds("native_out.rds", py_obj, file_format="binary", compression=None)

with open("native_out.rds", "rb") as f:
    assert f.read(2) == b"B\n"

Checklist before requesting a review

• I have performed a self-review of my code
• The code conforms to the style used in this package (checked with Ruff)
  -- (pre-existing lint errors)
• The code is fully documented and typed (type-checked with Mypy)
• I have added thorough tests for the new/changed functionality

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.66055% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.44%. Comparing base (5000127) to head (23f3802).
⚠️ Report is 10 commits behind head on develop.

Files with missing lines	Patch %	Lines
rdata/parser/_binary.py	88.88%	4 Missing ⚠️
rdata/tests/test_write.py	80.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #59      +/-   ##
===========================================
+ Coverage    94.42%   94.44%   +0.02%     
===========================================
  Files           19       21       +2     
  Lines         1992     2108     +116     
===========================================
+ Hits          1881     1991     +110     
- Misses         111      117       +6     

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[vnmabus]

Thanks for the PR, I will check it as soon as I can.

The code conforms to the style used in this package (checked with Ruff)
-- (pre-existing lint errors)

I fixed the pre-existing errors, the ones remaining are caused by the PR.