Add validators for cpuset_partition, sr_iov_boolean, sr_iov_uint32, managed_oom_mem_pressure_{limit,duration_sec}, dhcp_server_emit

[SJrX]

Goal

First of ~5 batches to extend the OptionValueTest burn-down buffer to last through July 2026. Each batch adds ~6 validators, each one buying ~1 day of buffer.

Targets (batch 1)

Function	Usages	C source	Notes
config_parse_cpuset_partition(0)	6	src/core/cgroup-util.c:134 (DEFINE_CONFIG_PARSE_ENUM_WITH_DEFAULT)	Simple enum: member/root/isolated/empty
config_parse_sr_iov_boolean(0)	6	src/shared/netif-sriov.c:549	Plain boolean via parse_boolean
config_parse_sr_iov_uint32(0)	6	src/shared/netif-sriov.c:393	Conservative uint32 (lvalue-specific bounds skipped)
config_parse_managed_oom_mem_pressure_limit(0)	6	src/core/load-fragment.c:4017	parse_permyriad — percent form only
config_parse_managed_oom_mem_pressure_duration_sec(0)	6	src/core/load-fragment.c:4055	parse_sec, must be ≥1s and not infinity
config_parse_dhcp_server_emit(0)	6	src/network/networkd-dhcp-server.c:827	Whitespace-separated list of IPv4 addresses or _server_address keyword

Skipped from candidate list

• config_parse_set_status(0) — accepts list of exit codes (0-255 + EXIT_* names) OR signal names (SIG* + numbers). Too many enum values to enumerate cleanly.
• config_parse_delegate_subgroup(0) — requires mirroring cg_needs_escape semantics; hard to validate cheaply.

Both can be revisited in a later batch if patterns emerge.