Silent truncation of user-provided data of type SQL_TEXT

[aafemt]

This is an initial architectural problem which surfaced after apply #8145.

For multibyte encodings engine validates data in input message limiting it to a supposed character length dsc_length / BPC. If an user has provided in the message metadata the real data length, this data gets truncated without even a warning.

Testcase is attached.

ctest.zip

[asfernandes]

The problem is #8145 then, and you were warned in #8082.

I see no sense in ask Pavel Zotov to test a change like #8566 that is not a fix, but a bug!

[aafemt]

I see no sense in ask Pavel Zotov to test a change like #8566 that is not a fix, but a bug!

Ok, consider it as a fix for #8145.