add back execute(optionsManager, dut) for chisel-dsp.

[sequencer]

In #1731, I removed the Driver.execute blindly, but I found the path is a little steep for legacy OptionsManager codes, this PR adds back execute(optiionsManager, dut) back to chisel3.stage.Stage to make chisel-dsp be able to compile, and deprecate this API, making the deprecation path smoother.

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
• Did you add appropriate documentation in docs/src?
• Did you state the API impact?
• Did you specify the code generation impact?
• Did you request a desired merge strategy?
• Did you add text to be included in the Release Notes for this change?

Type of Improvement

• new feature/API

API Impact

add chisel3.stage.chiselStage.execute(optionsManager: ExecutionOptionsManager with HasChiselExecutionOptions with HasFirrtlOptions, dut: () => RawModule)

Backend Code Generation Impact

none

Desired Merge Strategy

• Rebase: You will rebase the PR onto master and it will be merged with a merge commit.

Release Notes

add and deprecate API: chisel3.stage.chiselStage.execute

Reviewer Checklist (only modified by reviewer)

• Did you add the appropriate labels?
• Did you mark the proper milestone (3.2.x, 3.3.x, 3.4.0, 3.5.0) ?
• Did you review?
• Did you check whether all relevant Contributor checkboxes have been checked?
• Did you mark as Please Merge?

[jackkoenig]

This might be obviated by ucb-bar/dsptools#222