refactor: use 'H' std_logic state instead of custom pull up type

tests: rename startstop_condition_detector testbench to contain tb

tests: add messages to checks

tests: add pull up sda, scl behavior

tests: split master i2c functions to separata package

feat: add clear_buffer input to tx

tests: add slave testbench

fix: make slave work

feat: handle ack in rx, tx

feat(tx): remove unnecessary bit index

chore: use process(all) for combinational processes

tests: add tx testbench

tests: add rx testbench

tests: add startstop condition detector tests, fix behavior

tests: add test for address detector