README: Update the usage instructions

[lpawelcz]

@oharboe

This PR depends on The-OpenROAD-Project/bazel-orfs#27. Some of the instructions added here refer to GUI targets that are yet to be introduced to bazel-orfs. After merging The-OpenROAD-Project/bazel-orfs#27 we should pin new bazel-orfs version in MODULE.bazel and then merge this PR.

We also decided to remove Creating an issue report paragraph because we feel that it belongs to bazel-orfs documentation and will be added there alongside the support for make issue targets.
Perhaps most of the Tutorial chapter should eventually end up in bazel-orfs.
Please let us know what do you think.

[oharboe]

@lpawelcz all generic documentation on bazel-orfs should go into bazel-orfs. megaboom docs should contain little repetition of what is in bazel-orfs and mainly megaboom specific documentation.

[lpawelcz]

@oharboe moved Tutorial paragraph to bazel-orfs README in The-OpenROAD-Project/bazel-orfs#29.
We've left a small part of this tutorial in megaboom README to warn the users to use correct label when downloading the docker image with orfs_env target.

[lpawelcz]

CI failure is unrelated. To be fixed in #45.

[oharboe]

Let us just start with cleanup as a new baseline for documentation, even if there's more work to be done in bazel-orfs.