Create a coverage model for 40x Exceptions

Created by: silabs-robin

This PR adds an exceptions covmodel based on the "functional coverage" items of the exceptions vplan. The vplan was also tweaked to fix some simple problems and to reflect latest 40x spec.

Vplan Changelog:

• Updated phrasing "Breakpoint exception" to "Exception" for everything not breakpoint-related
• Updated "Environment call" to talk about "ECALL" instead of "EBREAK"
• Updated "Environment call" mcause from 3 to 11
• Removed "ecall over ebreak" priority item (it can't happen)
• Removed "pma over bus fault" priority item (it can't happen)
• Updated "Exception Priority" list to 40x latest UM
• Added new "Exception Priority" checks to combine exception causes
• Updated typos "exception2"->"exception" and "than"->"that"
• Updated "mtval" item to a TODO about 40x spec (mtval is TBD)
• Added items for instr/data-side trigger breakpoint