bond: align FromStr/Display strings with iproute2

[cathay4t]

• Change BondXmitHashPolicy Display/FromStr strings to match iproute2:
  "layer34"->"layer3+4", "layer23"->"layer2+3", "encap23"->"encap2+3",
  "encap34"->"encap3+4", "vlan-src-mac"->"vlan+srcmac"
• Add BOND_AD_ACTOR_PORT_PRIO constant and ActorPortPrio variant to
  BondAdSelect with Display/FromStr support

Unit tests for both BondXmitHashPolicy and BondAdSelect FromStr are
updated.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.14%. Comparing base (1fb4bd7) to head (099ba90).
⚠️ Report is 48 commits behind head on main.

Files with missing lines	Patch %	Lines
src/link/link_info/bond.rs	50.00%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #264      +/-   ##
==========================================
+ Coverage   68.10%   68.14%   +0.03%     
==========================================
  Files         144      146       +2     
  Lines       10103    10420     +317     
==========================================
+ Hits         6881     7101     +220     
- Misses       3222     3319      +97     

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[gemini-code-assist]

Code Review

This pull request updates the string representations of several BondXmitHashPolicy variants (e.g., changing "layer34" to "layer3+4") and adds support for the ActorPortPrio variant in the BondAdSelect enum. The review feedback recommends maintaining backward compatibility in FromStr parsing for the old BondXmitHashPolicy string formats to prevent breaking existing configurations, and suggests adding corresponding test assertions to verify this compatibility.

[gemini-code-assist]

To prevent breaking backward compatibility for existing configurations or scripts that use the old string representations, it is highly recommended to continue supporting the old strings (layer34, layer23, encap23, encap34, and vlan-src-mac) in FromStr parsing, while using the new format for Display. Additionally, to adhere to the project's line length limits, use a block expression for the longer match arm.

            "layer3+4" | "layer34" => Self::Layer34,
            "layer2+3" | "layer23" => Self::Layer23,
            "encap2+3" | "encap23" => Self::Encap23,
            "encap3+4" | "encap34" => Self::Encap34,
            "vlan+srcmac" | "vlan-src-mac" => {
                Self::VlanSrcMac
            }

References

1. Code formatting must adhere to the project's rustfmt configuration, especially the maximum line length. This may require using block expressions for what would otherwise be single-line match arms to stay within the configured limit. ^(link)
2. When converting from a string slice (&str) to a type where the conversion can fail, implement std::str::FromStr instead of From<&str>.

[gemini-code-assist]

Add assertions to verify that the old string representations are still parsed correctly for backward compatibility.

Suggested change

	assert_eq!(BondXmitHashPolicy::Layer34, "layer3+4".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Layer23, "layer2+3".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Encap23, "encap2+3".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Encap34, "encap3+4".parse().unwrap());
	assert_eq!(
	BondXmitHashPolicy::VlanSrcMac,
	"vlan-src-mac".parse().unwrap()
	"vlan+srcmac".parse().unwrap()
	);
	assert_eq!(BondXmitHashPolicy::Layer34, "layer3+4".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Layer34, "layer34".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Layer23, "layer2+3".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Layer23, "layer23".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Encap23, "encap2+3".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Encap23, "encap23".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Encap34, "encap3+4".parse().unwrap());
	assert_eq!(BondXmitHashPolicy::Encap34, "encap34".parse().unwrap());
	assert_eq!(
	BondXmitHashPolicy::VlanSrcMac,
	"vlan+srcmac".parse().unwrap()
	);
	assert_eq!(
	BondXmitHashPolicy::VlanSrcMac,
	"vlan-src-mac".parse().unwrap()
	);