### Description <!-- Required Add detailed description of what you are reporting. Good example: https://os.mbed.com/docs/latest/reference/workflow.html Things to consider sharing: - What target does this relate to? - What toolchain (name + version) are you using? - What tools (name + version - is it mbed-cli, online compiler or IDE) are you using? - What is the SHA of Mbed OS (git log -n1 --oneline)? - Steps to reproduce. (Did you publish code or a test case that exhibits the problem?) --> The number of compiler warnings has grown over time. Please consider implementing one or both of the following: - Improve documentation to encourage contributors to check for and resolve any compiler warnings before merge. - Add CI tests to enforce no compiler warnings allowed. (Preferred, I think.) Related: #7885, #6305 ### Issue request type <!-- Required Please add only one X to one of the following types. Do not fill multiple types. (Split the issue otherwise.) Please note this is not a GitHub task list; indenting the boxes or changing the format to add a '.' or '*' in front of them changes the meaning incorrectly. The only changes to make are to add a description under the description heading and to add an 'x' to the correct box. [X] Question [ ] Enhancement [ ] Bug --> [ ] Question [X] Enhancement [ ] Bug