Replace atomic unsafe pointers with generic atomic pointers

[Mihai22125]

Replace atomic unsafe pointers with generic atomic pointers.

First-time contributor, so any feedback is more than welcome!

This resolves: #157.

[CLAassistant]

All committers have signed the CLA.

[thorfour]

This looks great! Thanks for the contribution

[brancz]

Looks like we need to upgrade to go1.19, do you mind taking care of that @Mihai22125?

[Mihai22125]

Sure thing

[thorfour]

Error: sync/atomic is in the blacklist: Use go.uber.org/atomic instead of sync/atomic (depguard)

Looks like its necessary to update the .golangci.yml file

[Mihai22125]

Hi @thorfour, Thanks for the point.

I updated the .golangci.yml file. Can you check if it's alright now?

[thorfour]

   Error: copylocks: NewPartList passes lock by value: sync/atomic.Pointer[github.com/polarsignals/frostdb.Node] contains sync/atomic.noCopy (govet)
  Error: copylocks: literal copies lock value from next: sync/atomic.Pointer[github.com/polarsignals/frostdb.Node] contains sync/atomic.noCopy (govet)
  Error: copylocks: call of NewPartList copies lock value: sync/atomic.Pointer[github.com/polarsignals/frostdb.Node] contains sync/atomic.noCopy (govet)
  Error: copylocks: literal copies lock value from index: sync/atomic.Pointer[github.com/google/btree.BTree] contains sync/atomic.noCopy (govet)

Now it's mad about copying locks

[Mihai22125]

The errors should be fixed now, please let me know if there are any issues left.

[thorfour]

Closing in favor of https://github.com/polarsignals/frostdb/pull/203 thanks for the contribution @Mihai22125

[Mihai22125]

Hi! I'm glad I could help