OpenSystemsDevelopment / qpdf

Implements structural equivalence following ISO 32000-2 Annex J,
with a recursion depth limit (default 10) in place of cycle detection.
Handles numeric promotion, sparse arrays, streams, indirect references,
and null/uninitialized normalization. Includes tests in libtests/objects.cc.

Add a new configurable limit `--max-stream-filters` to address excessive stream filters in damaged or specially constructed PDFs. Update related documentation, tests, and release notes to reflect this feature.

…pport for configurable global limits via `qpdf_global_get_uint32` and `qpdf_global_set_uint32`.

- Standardize error handling by replacing repetitive throw statements with helper functions.
- Add test coverage for new helper functions in error handling.
- Enhance maintainability and readability with concise utilities.

Simplify integer value retrieval by introducing a templated `value` method in the `Integer` class. Replace redundant exception handling logic across multiple functions with this unified approach. Streamline type conversions and improve readability.

If duplicate keys are encountered, overwrite earlier values with the latest
value.

Also, reject them in strings.

Also. remove '.' as  starting char in lsTop.

When the schema wants a variable-length array, allow a single item as
well as allowing an array.

Call the parent container's item method before calling the child
item's start method so we can easily know the current nesting level
when nested items are added.

Bidirectional base64; will be used by JSON v2.