fix(common): specify alignment for COMP_ structs

When we read .kmx files, they have no alignment guarantees, so we need
to tell the compiler to generate unaligned-safe code for accesses to
`COMP_` structure members, because typically we point into the buffer
and read at any offset.

A .kmx file will generally be 2-byte aligned, as there are no structures
or data types with smaller than 2 byte widths. There is no requirement
that this be the case per the .kmx spec, though. So we use a 1 byte
alignment attribute for the compiler, so it will generate safe code when
reading these structs.

Note that we are assuming that `COMP_KEYBOARD` is aligned because it is
always the start of the file, so will be at the start of any buffer
which will automatically be aligned correctly.

We should probably review some of our design decisions and structs for
KMXPlus given this.