refactor: Standardize header guard macros.

[SharafMohamed]

Request

Decide on a standard for header guard macros.

Possible implementation

Two potential options for how we want to combine the snake case folder names and camel case file names (e.g. log_surgeon/finite_automata/DfaState) :

• 1. Ignore camel case (e.g., LOG_SURGEON_FINITE_AUTOMATA_DFASTATE).
• 2. Convert camel case to snake case (e.g., LOG_SURGEON_FINITE_AUTOMATA_DFA_STATE).

[LinZhihao-723]

Sorry to miss this in #57. We should also ensure the header guards are ended with the file postfix, e.g., DfaState.hpp should have its header guard being LOG_SURGEON_FINITE_AUTOMATA_DFASTATE_HPP