[LinearProgress] Add color="inherit" support

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

When using the component LinearProgress with the property color being the value inherit, the component throws the following error:

Cannot read property 'main' of undefined

Expected Behavior 🤔

It should inherit the color from the parent component (or use the default gray colors as seen on other components).

Steps to Reproduce 🕹

https://codesandbox.io/s/material-ui-v5-linearprogress-with-colorinherit-8w0xt

Context 🔦

I want to use the LinearProgress inside a Button and need it to inherit the color from the button.

Your Environment 🌎

`npx @material-ui/envinfo`

  System:
    OS: Windows 10 10.0.19042
  Binaries:
    Node: 15.12.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.10 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 7.7.6 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Chrome: Not Found
    Edge: Spartan (44.19041.423.0), Chromium (89.0.774.63) <- Browser used
  npmPackages:
    @emotion/react: ^11.1.5 => 11.1.5
    @emotion/styled: ^11.1.5 => 11.1.5
    @material-ui/core: ^5.0.0-alpha.28 => 5.0.0-alpha.28
    @material-ui/styled-engine:  5.0.0-alpha.25
    @material-ui/styles:  5.0.0-alpha.28
    @material-ui/system:  5.0.0-alpha.28
    @material-ui/types:  5.1.7
    @material-ui/unstyled:  5.0.0-alpha.28
    @material-ui/utils:  5.0.0-alpha.28
    @types/react: ^17.0.3 => 17.0.3
    react: ^17.0.2 => 17.0.2
    react-dom: ^17.0.2 => 17.0.2
    typescript: ^4.2.3 => 4.2.3

[itscharlieliu]

Can I take this issue?

[italodeandra]

Thanks for the contribution @itscharlieliu !