fix(Java): Improve Collection of Errors string

[texastony]

Issue #, if available:

Description of changes:
Collection of Errors is a frustrating error because it requires customer action
to completely serialize it into logs.

We can make a simple fix in Java to improve the CX,
by always serializing the list into the Collection Of Error's
message.

We concatenate the given error message with
a serialization of all the nested errors.

Squash/merge commit message, if applicable:

fix(Java): Improve Collection of Errors string

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[seebees]

This looks good. Thanks