Enable id->delay translation on all backends

[mtreinish]

Summary

The use of id as a gate equivalent to the single qubit gate delay on IBM backends has been deprecated for > 1 yr. As new backends are being released that do not support using id in this manner anymore we should be translating the id for IBM backends to the delay during transpilation otherwise users who manually insert id into their circuit on new backends without id as a supported gate will get a error. Additionally, Qiskit 0.23.0 will likely change the definition of IGate to be a typical identity which will be optimized away (or translated to Rz(0) if no optimization is specified) which will break user assumptions if they were manually using Id as a single qubit gate delay.

This commit enables default translation during transpile() by creating a separate translation stage plugin which is the default basis translation with the ConvertIdToDelay prepended to it. This plugin is then set as the default with the IBMBackend class using the backend default stage plugin hook points which override the default stage plugin to use during transplation when targeting the backend. This means if a user runs transpile() targeting an IBMBackend object on a cirucit that contains id gate it will be translated to delay as part of that process.

Details and comments

[mtreinish]

The docs failure will be fixed by #469

[coveralls]

Pull Request Test Coverage Report for Build 3823921282

• 6 of 13 (46.15%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 50.131%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit_ibm_provider/ibm_backend.py	1	2	50.0%
qiskit_ibm_provider/transpiler/plugin.py	3	9	33.33%

Files with Coverage Reduction	New Missed Lines	%
qiskit_ibm_provider/ibm_backend.py	1	59.31%

Totals
Change from base Build 3789927635:	-0.02%
Covered Lines:	2871
Relevant Lines:	5727

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💛 - Coveralls

[taalexander]

LGTM