generate_tri_treatment_from_two_covariates: Generate three-valued treatment with constraint on
In kaz-yos/empeq3: Conduct three-group empirical equipoise study

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1 2	generate_tri_treatment_from_two_covariates(X, alpha01, alpha02, alphaXm1, alphaXm2, gamma, sigma)

`X`	data_frame containing two covariates
`alpha01`	True intercept for the first linear predictor.
`alpha02`	True intercept for the second linear predictor.
`alphaXm1`	True coefficients for the first variable for the first linear predictor.
`alphaXm2`	True coefficients for the first variable for the second linear predictor.
`gamma`	Ratio of the true coefficient for the second variable and the first variable.
`sigma`	scaling of all covariate effects. A higher value means stronger covariate effects, i.e., less clinical equipoise.