Remove methods duplicated in `go1.19` `sync/atomic`

Since the go1.19 update, there are lots of duplicate functionality between this package and sync/atomic. This duplication is currently needed because go1.18 is still supported.

sync/atomic has the following types that are duplicated here:

• Bool
• Int32
• Int64
• Pointer[T]
• Uint32
• Uint64
• Uintptr

All types in sync/atomic have the following methods:

• CompareAndSwap
• Load
• Store
• Swap

Integer-like types have the following, in addition to the above:

• Add

But there is still some functionality in here go.uber.org/atomic that is not there in sync/atomic.

All thing considered, after go1.18 becomes unsupported, we could do the following:

• Update gen-atomicint to embed sync/atomic types. Only the following additional methods
  need to be kept.
  - CAS (Deprecated)
  - Dec
  - Inc
  - Sub
  - String
  - MarshallJSON
  - UnmarshallJSON
• Update Bool to embed sync/atomic type. Only the following additional methods
  need to be kept.
  - CAS (Deprecated)
  - String
  - Toggle
  - MarshallJSON
  - UnmarshallJSON
• Update Pointer[T] to embed sync/atomic type.

I just wanted to document all this stuff before I forget.

Start with the gen-atomicint entry point and review the existing Bool and Pointer[T] implementations alongside the generated atomic integer types. Compare their methods with the Go 1.19 sync/atomic types. Done means the duplicated methods are provided through embedded sync/atomic types while the listed additional methods remain available.