MEDIUM: otel: added CLI commands for runtime filter management

MEDIUM: otel: added CLI commands for runtime filter management

Added HAProxy CLI commands that allow runtime inspection and modification
of OTel filter settings without requiring a configuration reload.

The new cli.c module registers CLI keywords under the "otel" prefix and
implements the following commands: flt_otel_cli_parse_status() displays a
comprehensive status report of all OTel filter instances including filter
ID, proxy, disabled state, hard-error mode, logging state, rate limit,
analyzer bits, and SDK diagnostic message count;
flt_otel_cli_parse_disabled() enables or disables filtering across all
instances; flt_otel_cli_parse_option() toggles the hard-error mode that
controls whether errors disable the filter for a stream or are silently
ignored; flt_otel_cli_parse_logging() manages the logging state with
support for off, on, and dontlog-normal modes; flt_otel_cli_parse_rate()
adjusts the sampling rate limit as a floating-point percentage; and
flt_otel_cli_parse_debug() sets the debug verbosity level in debug builds.
All modifications are applied atomically across every OTel filter instance
in every proxy.

The CLI initialization is called from flt_otel_ops_init() during filter
startup via flt_otel_cli_init(), which registers the keyword table through
cli_register_kw().

Supporting changes include the FLT_OTEL_U32_FLOAT macro for converting the
internal uint32_t rate representation to a human-readable percentage, the
FLT_OTEL_PROXIES_LIST_START/END iteration macros for traversing all OTel
filter instances across the proxy list, and flt_otel_filters_dump() for
debug logging of filter instances.