feat(pe): add parse_imports option to ParseOptions

[supervacuus]

Parsing PE import tables is expensive: for each DLL, the parser does a full pass over the import lookup table (resolving every symbol RVA via a linear scan over sections), a second pass over the import address table, and then a third reshaping pass in Import::parse. For binaries with large or malformed import tables, this adds up fast, especially when the caller only needs headers, debug info, or exports.

This PR adds a parse_imports flag to ParseOptions (default: true) with a with_parse_imports builder method, allowing callers to skip import table parsing entirely. When set to false, import_data, imports, and libraries remain empty while everything else is parsed as usual.

This is a follow-up to #506 (#508).

[supervacuus]

Just wanted to ping if this kind of change is of interest.

I have also now added a new PR (#527) that fixes the underlying issue. It might still make sense to be able to turn off import parsing, but if #527 is accepted, I could understand if you didn't want to add another parser option. The resulting runtimes are now essentially the same for either PR.