changed basis from char to enum

[MadhuMPandurangi]

This is the test result. Shows successfully passed all test cases. This PR is regarding Issue #476
`[----------] Global test environment tear-down

[==========] 183 tests from 31 test suites ran. (969 ms total)

[ PASSED ] 183 tests.

make[1]: Leaving directory '/workspaces/quisp/quisp'`

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This change is 

[zigen]

thanks for contribution!
could you check my comment and fix, commit and push it again?

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @MadhuMPandurangi)

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quisp/modules/QNIC/StationaryQubit/StationaryQubit.cc line 253 at r1 (raw file):

  if (rand < 1.0 / 3) {
    outcome.outcome_is_plus = qubit_ref->measureX() == EigenvalueResult::PLUS_ONE;
    outcome.basis = backends::abstract::Basis::X;

you can declare using backends::abstract::Basis on top of the .cc file, and use it like Basis::X.

[zigen]

and clang-format step is failed, could you run $ make format to format your code?

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @MadhuMPandurangi)

[MadhuMPandurangi]

Declaring using backends::abstract::Basis on top of the .cc file is done and $ make format command is executed. But I'm getting errors in simulation test. As we discussed in slack i'm going through the simulation
Thank you

[zigen]

Reviewed 4 of 4 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MadhuMPandurangi)

[MadhuMPandurangi]

Reviewed 4 of 4 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @MadhuMPandurangi)