"FCOL" non-MCM 8-bit palette entry text mode

[dansanderson]

Is your feature request related to a problem? Please describe.
Normal text mode can select a primary color from any of the first 32 palette entries using color bits 0, 1, 2, 3, and 6. It'd be nice to have a mode that disables attributes in favor of using all eight color bits to select a character's primary color from palette entries 0-255 (in normal bit order).

Describe the solution you'd like
FCOLMCM D063.6 enables using all eight color bits to select the palette entry, but only if MCM is also enabled. MCM disables char attributes, uses only the lower four bits for the palette entry (0-15), and also repurposes bit 3 to select low-res multicolor mode for the character. Combined with FCOLMCM, it gets eight bit foreground color (0-255), retaining the bit 3 behavior. FCOLMCM & ~MCM currently does nothing.

FCOLMCM & ~MCM should be a normal (non-SEAM) text mode that disables character attributes and uses all eight bits to select a palette entry from 0-255 for the character foreground color. It'd be just like FCOLMCM & MCM, but with no special bit 3 behavior.

(This should also be supported in Extended Background Color Mode (ECM), which has nothing to do with the color byte.)

Additional context
Looks like there's some related discussion on issue 571 but not a direct answer. The viciv.vhdl on this is easy to read but doesn't represent the history of the design. I assume D063 is not a VIC-III compatibility concern. I wonder if we backed into this feature and just didn't make the connection that it could be useful in non-MCM text mode?

[dansanderson]

kibo appears to be discovering that this should already be a feature, and we just have errors in our implementation. #922

Specifically, MCM should not be disabling attributes. ATTR does disable attributes, but should also be replacing attr bits with color bits. If we fix these, then we don't need to define FCOLMCM + ~MCM.