Speed up 1Q/2Q RB (#982)

Improve the performance of transpiled circuit generation in 1Q/2Q StandardRB/InterleavedRB (about 10x speedup in 1Q SRB/IRB and 5x speedup in 2Q SRB/IRB in most cases).

Including following feature pull-requests:
* New algorithm for RB building Cliffords by layers (#892)
* Improve custom transpilation for faster 1Q/2Q RB (#922)
* Improve integer-based Clifford operations for 1Q/2Q RB (#940)
* Readd support for backends with directed basis gates to RB experiments (#960)

Features other than speedup:
* Fix performance regression in 3 or more qubits RB (embedded at Refactor RB module for future extensions #898)
* Improve validation of interleave_element in InterleavedRB
* Restructure tests for RB module
* Remove the barriers in front of the first Cliffords in RB circuits

Co-authored-by: merav-aharoni <[email protected]>
Co-authored-by: Naoki Kanazawa <[email protected]>

MANIFEST.in

@@ -1,3 +1,5 @@
 include LICENSE.txt
 include requirements.txt
 include qiskit_experiments/VERSION.txt
+include qiskit_experiments/library/randomized_benchmarking/data/*.npz
+exclude qiskit_experiments/library/randomized_benchmarking/data/generate_clifford_data.py