feat: support merging object/map attributes

[bbckr]

Allows optionally merging map keys in block attributes whose value is a map. When unset/false (which is the default), the two maps that will be merged will be overridden with the second map value. When set to true, the keys of the maps will be merged. In other words, for now merging is one level deep given how attributes are represented in HCL, which is a list of tokens. This could eventually be expanded to do a recursively merge on the map values, but this is left out for now.

The interface is non-breaking, since the exported TS merge function optionally allows options to be set. Should behave as normal.

On top of the added functionality, the changes include:

• Creating a new struct to house the Go Merge function.
• Creating new structs and classes for the MergeOptions in Go and TS.
• Updated all tests and added additional test cases.