turn off default prompt styling (bold) to prevent leakage

[fdncred]

Before this PR, the bold attribute was hard coded and therefore leaked through. Example:

Before

Notice that the prompt is green bold even though I told it just green. Also, when i draw the prompt with the do command, it's drawn right. This is because the do command is rendering a buffer and the PROMPT_COMMAND is going through this code in reedline and hard-coding bold everywhere.

After

Notice that when i tell it green, the prompt is drawn in green and with the do command. When I tell it green_bold the prompt is drawn in green_bold as well as with the do command.

This is meant to close nushell/nushell#9123 when it's implemented in nushell.

[sholderbach]

Yeah this styling should have no business being part of the Painter. With Prompts being also just strings as in the nushell case we should not set style here.

I think we could reconsider even the whole prompt color thing.

Before we land please keep the reset defensive.