Readonly span support

[ChrisMcKee]

Changes

Spans buffers and spans

Adds new methods that allow passing in a buffer

CreatePasswordHash(ReadOnlySpan<char> inputKey, ReadOnlySpan<char> salt,
        Span<char> outputBuffer, out int outputBufferWritten,
        HashType hashType = HashType.None,
        EnhancedHashDelegate enhancedHashKeyGen = null)

Adds in buffer zeroing when no longer needed to reduce time in memory.

Changed targeting and csproj defined constants to ensure net8 still gains the available support for span that came with the memory package and netstandard support. This could potentially start at 4.7.2 but the netstandard integration was iffy.

Validate input length (Breaking)

If the usage doesn't make use of the enhanced hash generation to retain entropy (aka the standard use) the library will throw when the input to hash length is greater than 72 chars.
This isn't standard behaviour in most bcrypt libraries where truncating silently is the default.
But I believe this is necessary, should always have been in place, and will force developers to decide deliberately to truncate input at 72 if they wish to retain existing behaviour.

Enhanced Hashing V3

• Split 'enhanced' versions into separate classes
• Swap func for delegate
• Add span based calls

Along with switching the func to a bog standard delegate, splitting the enhanced versions into separate classes simplified maintaining the previous versions and adding in the new version.
The v3 enhanced hash adds in keyed HMAC which apart from protecting against theorical risks of shucking adds a further uniqueness to the produced key material.

Experimental SafeString support

Hate SafeString, it's filled with lies and was really only a useful feature in Windows. In an API it should never be touched but there are some cases in Windows apps where people still require it to tick a box so I've added a sort of basic implementation
This code requires unsafe enabled so will probably be disabled initially.

SecureEquals check

This basically needed to be made for the span handling but also allowed a few minor optimizations which mimic the code in the .net codebase.

Net 10

We basically try to tag against the lts releases; the code may be updated to target sts between releases to assertain if there is any performance improvement worth having but otherwise its lts.

Examples

The api uses the identity extension to enable bcrypt passwords; chucked in a maui to test performance on android as we've been asked before by people doing the hashing at the device level

Release Benchmarks

Separate project that tests previous nuget package versions; its mostly as a simple way to test for regressions in performance while the other benchmark project is for testing components in a more targeted way.