Unexport some bson types

[AlekSi]

Refs #260.

[codecov]

Codecov Report

Merging #280 (d32c200) into main (af6c993) will not change coverage.
The diff coverage is 51.06%.

@@           Coverage Diff           @@
##             main     #280   +/-   ##
=======================================
  Coverage   51.05%   51.05%           
=======================================
  Files         112      112           
  Lines        5347     5347           
=======================================
  Hits         2730     2730           
  Misses       2205     2205           
  Partials      412      412           

Impacted Files	Coverage Δ
internal/bson/bson.go	0.00% <0.00%> (ø)
internal/types/types.go	94.11% <ø> (ø)
internal/bson/document.go	45.39% <45.45%> (ø)
internal/bson/datetime.go	67.85% <66.66%> (ø)
internal/bson/binary.go	57.89% <75.00%> (ø)
internal/bson/bool.go	60.00% <75.00%> (ø)
internal/bson/int32.go	68.18% <75.00%> (ø)
internal/bson/int64.go	68.18% <75.00%> (ø)
internal/bson/objectid.go	65.00% <75.00%> (ø)
internal/bson/timestamp.go	68.18% <75.00%> (ø)
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update af6c993...d32c200. Read the comment docs.