Add a setting to switch auto-bonding off

[paulsmirnov]

Is your feature request related to a problem? Please describe.
We got a request for this feature from one of our users.
Their files contain sparse atoms depicting a cavity. They are not really forming a full molecule so there's no need (and no way) to reconstruct chemical bonds. Currently, the algorithm crashes, and that is worth a separate bugfix (TBD). However, even if it doesn't, bonds should not be built.

Describe the solution you'd like
Currently, auto-bonding depends on an internal flag that depends on the file format. It would be helpful if we could disable auto-bonding no matter what format is used. A short discovery might be needed but of the top of the head there could be a setting autobonding with options:

• "default" or undefined: keep the old behavior,
• "disable": don't reconstruct bonds for any format,
• "force": reconstruct bonds for all formats,
• "nohetatm": exclude HETATM records from auto-bonding (currently, they are still included unless they already have bonds).

Describe alternatives you've considered

• Use the format that doesn't reconstruct bonds (SDF, MOL, CML, MMTF).
• Avoid crashing (try/catch?) and proceed without bonds if algorithm fails.

Additional context
To be provided by the user if any.