fix all errors and warnings using dialyzer and eunit

[joergen7]

This pr performs quality of life improvements making the following commands run without errors or warnings:

rebar3 eunit
rebar3 dialyzer

Missing Function Specs

Observation

Running rebar3 eunit emits warings about missing function specs for all test generators:

Warning: missing specification for function parse_main_test_/0

Execution

This pr adds function specs for the test generators.

Fix rebar.config

Observation

Running rebar3 dialyzer emits the following error:

===> Could not find application: hipe

After removing hipe from dialyzer's dependency set, the following error occurs:

Unknown function asn1rt_nif:decode_ber_tlv/1

Execution

This pr removes hipe and adds asn1 to dialyzer's dependency set.