Some attribute implementations not matching VIC-III behaviour

[ki-bo]

Test Environment (required)
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• Platform: MEGA65
• Core Commit: 0.97
• ROM Release: 920417

Describe the bug
The VIC-III attributes implemented on the MEGA65 do not behave as on a real VIC-III. These are the differences:

1. Blinking of characters is much slower. On VIC-III, blinking frequency is the exact same as the screen editor's cursor.
2. The highlight bit (bit 6) should use palette colours $10-$1F instead of $00-$0F for both character foreground as well as background colour. On VIC-IV, the foreground colour is taken from palette $1x while the background colour still is taken from the $0x range.
3. If enabling both highlight (bit 6) and reverse (bit 5), the character should swap fg and bg colour. This is correctly implemented on VIC-III, but not on VIC-IV. It is working correctly if highlight is not enabled, but there is no reason why it should not work in combination with that bit.

To Reproduce
Steps to reproduce the behaviour:

1. Execute the attached asm program with VIC-III and VIC-IV and check the differences

attr_test.zip

Expected behaviour
See attached screenshots for the two states with a real VIC-III chip (CSG 4567R5).

Additional context
Note that the palette definition is the same for the first 16 colours on C65 and MEGA65, but the second set of 16 colours ($1x) is different. This is intentional and is not the problem here.
In the attached test program, I explicitly set color $16 to black, as 6 was set as background color. Enabling highlight should use $16 as bg colour instead of $06, which indeed is the case on a VIC-III (and also is defined in the C65 specification document).