pgsql: PostgresNode: add backup_fs_hot and backup_fs_cold

PostgresNode: add backup_fs_hot and backup_fs_cold

These simple methods rely on RecursiveCopy to create a filesystem-level
backup of a server.  They aren't currently used anywhere yet,but will be
useful for future tests.

Author: Craig Ringer
Reviewed-By: Michael Paquier, Salvador Fandino, Álvaro Herrera
Commitfest-URL: https://commitfest.postgresql.org/9/569/

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/28f6df3c36769eedce5c73d2f5bab9892d5cd76e

Modified Files
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src/test/perl/PostgresNode.pm | 94 ++++++++++++++++++++++++++++++++++++++++---
1 file changed, 88 insertions(+), 6 deletions(-)