Pylas

- Added Support for Scaled Extra bytes

- Added more type hints, which in combination to others changes
should help IDEs provide better autocompletion.

- Added pylas.LazBackend to be able to select the backend to use if
many are installed

- Changed support for the laszip backend to now use
bindings to the laszip c++ API instead of using
the laszip executable found in the PATH

- Changed simplify EVLR
Previously we had a EVLR class which was just a VLR subclass.
Now EVLR are just VLR, kepts in a different list, and written
as EVLRs if there are any.

- Changed: VLRList now subclass list

- Changed Header classes & Vlr
The hierarchy of header classes (RawHeader1_1, RawHeader1_2, etc)
is removed and now only one class exists LasHeader, where most
of the fields that reader/writers care about are removed and
field that user care about are kept and put in user-friendly classes.

The vlrs are now also a part of the header
(it simplifies synchronizing, the header, vlrs, point_format and extra bytes vlr)

- Removed pylas merge

- Added write ('r') and append ('a') mode to pylas.open
- Added ability to read a LAS/LAZ file chunk by chunk
- Added ability to write as LAS/LAZ chunk by chunk
- Added ability to append points to LAS/LAZ (LAZ only with lazrs)

- Added SubFieldView class to handle LAS fields which are bit fields
(e.g. return_number) in a more consistent way than was done.

- Removed lazperf support for compression/decompression

- Added maximum version to the lazrs optional dependency to 0.2.0.

- Fixed writing LAZ file with EVLR when piping through laszip.exe

- Added support for compressing & decompressing with laz-rs (supports parallel processing)
- Added support for compressing using laszip.exe
- Added Overflow & Underflow checks to the scaled x, y,z setters

- Allow adding extra bytes to all las versions
- Added rounding of x, y z coordinates when they are set