Add `Key=Value` table `coder_parameter` type

[djarbz]

I would like to add a way to allow users to create workspace specific EnvVars and Secrets.

I am envisioning a table like input with keys in the first column and values in the right.
In the terraform definition, we can optionally select to mask the values for secrets.
Optionally, show the "eyeball" to unmask the value.
When the end user types in a row, a new row will automatically be added so that the number of KV pairs can be dynamically growing.

For secrets:

Key	Value
API_KEY	********

For EnvVars:

Key	Value
API_HOST	api.coder.com
RUN_ENV	DEV