Fix #1055 allow multiple validators with cast for the same field

[rochacbruno]

from dynaconf import Dynaconf
from dynaconf import Validator

settings = Dynaconf(var="dynaconf")

def a(v):
    print("called a, replace conf -> settings")
    return v.replace("conf", "settings")

def b(v):
    print("called b, transform to upper DYNASETTINGS")
    return v.upper()

validators = [
    Validator("var", cast=a),
    Validator("var", cast=b),
]

settings.validators.register(*validators)
settings.validators.validate_all()

assert settings.var == "DYNASETTINGS", settings.var

Fix #1055

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[github-actions]

Test Results (Python 3.10)

475 tests  ±0   475 ✔️ ±0   34s ⏱️ -1s
    1 suites ±0       0 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 3f4c41a. ± Comparison against base commit b528e92.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results (Python 3.8)

475 tests  ±0   475 ✔️ ±0   35s ⏱️ +3s
    1 suites ±0       0 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 3f4c41a. ± Comparison against base commit b528e92.

♻️ This comment has been updated with latest results.

[github-actions]

Test Results (Python 3.11)

475 tests  ±0   475 ✔️ ±0   34s ⏱️ -2s
    1 suites ±0       0 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 3f4c41a. ± Comparison against base commit b528e92.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.75%. Comparing base (b528e92) to head (3f4c41a).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1080   +/-   ##
=======================================
  Coverage   98.75%   98.75%           
=======================================
  Files          23       23           
  Lines        2248     2249    +1     
=======================================
+ Hits         2220     2221    +1     
  Misses         28       28           

☔ View full report in Codecov by Sentry.
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[pedro-psb]

Otherwise LGTM