RFC: rpc: Support time specifiers in dumpwallet filename #14887

Support strftime specifiers in dumpwallet filename.

Example:

bitcoin-cli -regtest dumpwallet "/tmp/wallet_%Y%m%d_%H%M%S.bak"

{
  "filename": "/tmp/wallet_20181206_155742.bak"
}

See http://www.cplusplus.com/reference/ctime/strftime/.

Follow up of #9937.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #14599 (Use functions guaranteed to be locale independent (IsDigit, ToLower) in {Format,Parse}Money(...), uint256::SetHex(...), etc. Remove the use of locale dependent boost::is_space(...) by practicalswift)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

The client can also build the final path.. :roll_eyes:

Yeah, seems like unnecessary complexity to pull in

Agree.