feat(theme-generator): Add possibility to force custom color @angular/material:theme-color

### Feature Description

My problem is that I still can't understand how `@angular/material:theme-color` works. In the terminal, I need to provide colors for primary, secondary, and tertiary. For each one, I specify a single color, like #ff9500, because that's what I want.

`What HEX color should be used to generate the M3 theme? It will represent your primary color palette. (ex. #ffffff) **#005dba**
What HEX color should be used represent the secondary color palette? (Leave blank to use generated colors from Material) **#005dba**
What HEX color should be used represent the tertiary color palette? (Leave blank to use generated colors from Material) **#005dba**`

However, when generating the theme, I see that it creates color palettes, but when I try to get just my color, I use **`--mat-sys-primary`.** Unfortunately, it appears significantly darker (#8c5000), and I don't know which variable the color is actually hidden under. I have the impression that due to the low contrast, it is being artificially darkened. However, I selected the option not to generate mixins with high contrast. I would like to be able to use exactly that color without worrying about contrast. Currently, I am forced to manually change all the system token colors because the generated palette still interferes too much with what I want to achieve, taking away the flexibility I need in this case.

### Use Case

It would be great to be able to specify in the terminal that I want exactly the colors I mention, without any interference.

从 @angular/material:theme-color 生成器及其终端提示开始，然后将请求的颜色与生成的 --mat-sys-primary 值进行比较。当用户可以选择完全使用指定的颜色，而不会被生成的调色板或对比度调整覆盖时，即表示完成。

由索引模型根据 Issue 内容生成。