Remove obsolete sysui lint tools

The lint tools in packages/SystemUI/tools/lint no longer worked, and
they were not being used for upload hooks as the comments suggested.

The new way to run lint manually is via Soong. Append '-lint' to the
relevant Soong module (the one that has the extra_check_modules
pointing to "SystemUILintChecker"), then use aninja to list the
path.

For example,

 $ m SystemUI-core-lint
 $ aninja -t query SystemUI-core-lint
SystemUI-core-lint:
  input: phony
    out/soong/.intermediates/frameworks/base/packages/SystemUI/SystemUI-core/android_common/lint/lint-report.xml
  outputs:

Then, in the out/soong/.../lint directory, there will be an html report
and lint-baseline.xml file.

Bug: 398194411
Test: m SystemUI-core-lint && aninja -t query SystemUI-core-lint
Flag: EXEMPT lint only
Change-Id: I0b8a7a647159aaa06f7efba8defb25dc1fd15e27