`labels` argument fails to rename with `etable`, `iplot`, `coefplot` for interactions

[s3alfisc]

With interacted variables, the labels argument fails for al three functions above as reported by mortizm1988 in #892.

Example:

%load_ext autoreload
%autoreload 2

import pyfixest as pf
from pyfixest.report.utils import rename_categoricals, rename_event_study_coefs
import numpy as np

df = pf.get_data()
fit1 = pf.feols("Y ~ i(f1, X1)", data = df)
fit2 = pf.feols("Y ~ i(f1, X1) + X2", data = df)

pf.etable(
    [fit1, fit2], 
    labels = {"C(f1)[0.0]:X1":"var 1"}, 
    type = "md"
)

# index                   est1        est2
# ----------------  ----------  ----------
# depvar                     Y           Y
# ----------------------------------------
# C(f1)[0.0] x X1   -1.032***   -1.000***
#                      (0.249)     (0.238)
# C(f1)[1.0] x X1      0.541*     0.576**
#                      (0.224)     (0.214)
# C(f1)[2.0] x X1   -1.767***   -1.834***

Works for non-interactions instead:

fit1 = pf.feols("Y ~ i(f1)", data = df)
fit2 = pf.feols("Y ~ i(f1) + X2", data = df)

pf.etable(
    [fit1, fit2], 
    labels = {"C(f1)[T.1.0]":"var 1"}, 
    type = "md"
)

# index                est1        est2
# -------------  ----------  ----------
# depvar                  Y           Y
# -------------------------------------
# var 1           2.544***    2.544***
#                   (0.431)     (0.414)
# C(f1)[T.2.0]   -1.635***   -1.631***
#                   (0.452)     (0.434)
# C(f1)[T.3.0]      -0.464      -0.305

[s3alfisc]

I actually figured out how to make this work!

We'd have to rename the "categorical" part of the interaction, not the "full" interaction. Rule of thumb: always only rename a variable, not two that jointly form a coefficient =) Here is an example what I mean by this:

import pyfixest as pf
from pyfixest.report.utils import rename_categoricals, rename_event_study_coefs
import numpy as np

df = pf.get_data()
fit1 = pf.feols("Y ~ i(f1, X1)", data = df)
fit2 = pf.feols("Y ~ i(f1, X1) + X2", data = df)

pf.iplot(
    [fit1, fit2], 
    labels = {"C(f1)[0.0]":"var 1"}, 
)

produces

So use labels = {"C(f1)[0.0]":"var 1"}, instead of labels = {"C(f1)[0.0]:X1":"var 1"}`.

Note sure if this is really too straightforward? At the very least, we should update the docs. Would you have expected such behavior @mortizm1988? What are your thoughts on this @dsliwka? Maybe just clarifying in the docs is "good enough"?