Use dynamic memory for connection strings handling. (#323)

* Fix cli_list environment variable parsing.

Arrange to share more code from cli_common, and in passing introduce a new
structure to handle the bytes and bytesPretty within a single unit.

* Review Postgres URI handling and parsing APIs.

Make the internal parsing APIs use dynamic memory, and then keep a single
instance of the connections strings, safe versions of them (without the
password), and the password separated in-memory.

* Only compute safeURI when logging the connection string.

* Use pg_strdup and removed NULL checks

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Co-authored-by: Chanderprabh Jain <chajain@microsoft.com>
Co-authored-by: cpj2195 <chanderprabhjain95@gmail.com>