build(deps): fix compilation errors by downgrading picky and related crates

The dependency update from dependabot introduced picky 7.0.0-rc.20, which has
breaking API changes incompatible with sspi versions used by IronRDP.
Downgraded picky and related crates to their previous versions:
- picky: 7.0.0-rc.20 -> 7.0.0-rc.15
- picky-krb: 0.11.3 -> 0.11.0
- picky-asn1-der: 0.5.4 -> 0.5.2
- picky-asn1-x509: 0.14.6 -> 0.14.4
- now-proto-pdu: 0.4.2 -> 0.4.1
- proxy_cfg: 0.4.2 -> 0.4.1

Also ran `cargo update` to update all other dependencies to their latest
compatible versions.

Co-authored-by: CBenoit <3809077+CBenoit@users.noreply.github.com>

Author: Copilot