Performance improvements w/Span API

Highlights

@AlgorithmsAreCool Added benchmarks for better visibility on performance #119
@AlgorithmsAreCool Introduced Span for much better native interop performance #122
Uses Github Actions and covers more OS variations
Updated native lmdb libs to 0.9.24

Upgrade instructions for those coming from pre-span changes.

MDBValue now makes itself more prominent in the public API. It exposes two new methods CopyToNewArray, and AsSpan. If you simply want older code to work and compile again, CopyToNewArray is what you're looking for. If you want to squeeze more performance, spend some time with AsSpan.

0.8.14

• lmdb updated from master
• Fixed CompareFunction being collected by GC

0.8.12

• Implemented mdb_set_compare and mdb_set_dupsort
• Implemented cursor operations: multiple put, get multiple, move next multiple
• DatabaseOpenFlags.DuplicatesFixed now include DuplicatesSort by default
• MoveNextDuplicate and MovePrevDuplicate now return only value
• Actualised CursorPutOptions and PutOptions
• Added missing to-bytes converters
• API improvements and changes

0.8.8.52157

• Added missing PutOptions
• Added compact option to LightningEnvironment.CopyTo

0.8.7.52133

• Fixed concurrency issues with CursorManager & TransactionManager
• Added missing environment open flags
• Fixed LightningEnvironment.UsedSize calculation logic

0.8.6.51452

• Added LightningTransaction.GetEntriesCount
• Added LightningEnvironment.PageSize, LightningEnvironment.UsedSize, LightningEnvironment.EntriesCount
• Fixed incorrect default map size value

0.8.5.51145

• LMDB updated from master (ver. 0.9.15)
• Internal resources management refactoring
• Minor bug fixes

0.8.3.52343

Updated lmdb vesion

0.8.2.51054

Added docs and enchanced API

Lightning.NET 0.8.1.52127

Fixed some typos

Closes #23