[Feature] How to make a piecewise visual map scrollable/multi-line layout, just like the legend

### What problem does this feature solve?

[demo](https://echarts.apache.org/examples/zh/editor.html?c=line-simple&code=PYBwLglsB2AEC8sDeAoWsDGwA2wBOAXLANprqwDkAxACwDMA7AJwDCAohQDRnrVNMAhABwAxAIxcelKiICCAEQGNJ5aSJZCAbAAYATCvLURchjSEHeVBroEBWNgIvSGQlvLbyn1WSyay2-tyqRj50miJeMvIMIjEUZAC6QbAAnrIAHhAAzkSoqmApIACmRBQAbgCG2ACuRU4gwFkQkDCl2EUAZmBOFZlZADIVAEZF2LlS6AAWEAAmRQDyZUV42BUgRGB4tcmqHTBgAMoQAF4lsGJiO-RZk8AA7htbRVIAvlc394-1ZG9k6RnZcb5QpnCgYCpgIoAc3wKXqjWaUGgpSGwDAYGAAFsnB8HrBNtspL1soMRmNkBNYHtoIcTmcLq8fsksssIEUciQpHlVPiQSiKngnOgWe0MJCZgBZYBzUqY6rYSAgdpC2BFTEgSYVJoc7k82DNNUHArtIF68igCoYZopIjaAB0TEp6BelN-epFRTFpr1BsxRpSJopZvNIEt1qIlyd5FReDmeAAKnzKFkcLMVaoY3GAOqzMCTIi6KNus2rMnes0Wq0FCNF11XdDQCqY0GAN7TAHSqgHe5FVFaBYGVBs02khiJJR9JEYjaBKuxnoUfoKF4WbljHrWBCK7tLpEDdSJdQyZgHdXVHorFEOi71RYGkVCDQUmjL7PZ3JDE4RUr_dQ5alYlZJwbw6e8zgJIorn_AAFYB70hQgB2BYpSmgGA6led5bjxMCmTIIYthuFdgBwVFxxICg8E9bpp1fMh32wEjy1xIgOiqFkcIXPA1mmDAJ3nWAZghLUiiPTlVF1a5gGqPAMCKAAJIoKjjZjWPAykZggZtoCaGAOVIYNxL1DoZgASRmZCMA6JgiiYS8mCEDAZgwGhNDEZghgYbRrJodNyEbZtSkAMVVAEGVQAwJUAbx8fPQAokMofB1MbbBItgY5UMTGLyPueJg2LPUDJ5PzW07JK9jwTEIVyHKzWi0EOlwCEkpS6AijS0Fm02CAMCys1KrEqMGybUFgsAWBVAAfPYr8DKkSkB6nlqtKOL7yqBrUqTMEcHwAQ4VrPU-NUFMpJkico2IChADRlQAwzQizhzjMWxtGuig7qhQBT00AGnNAEYrQBGoMACbdADLbQBuW0AEoDABx0ihdp5E7AArlQB-I0AWUTAEzTLhYE0XRdAe2wmG0TFsEARcTAGMfQB8V0AXqMwfrcgTsAN01AEifK713oOgHpoXRtChQBDEMAEBDAFcHanSeOihAHDNQAfPUAClcgqRsRtDoO6HsAX01AHFNQA3DJlwAV80AIATAA6_QB-HUAE4iACpAFo5QBADzuwBxJ154MTue0XabEOhtAYWx0e0LHsEATJtAGLtQAr1MAPVjABKjQAnIMAdFtAEXlQAmdPNs0TsACHNAB9M2ndDMGgHsATMzAHo7QAlA2TwBYeUAQblY4jvUTsAfYdACVEm3dFcx3KCLgBaQBI50AKrsi8AL8VAGPlQBRiILiGKEAe2CgpthhrCr3ua4lqFAHb9QBftUAAc9AHKPQATNMAEtdAHjArvVBOwB9jP7pGpcl3Q7WH5PADBAwAxGJrwBSoMAYvjPoJtfyYoQA7TPhm2JfuyhAGY0wBJRUANmDAARMwBQ5UAAfmgAaq0AIg6gAcVzBpScGLo5zJDKNkaoVQJRrCOr1H0kI_QpExKickYIIDSWVGTSE6QwAAHFUGwEdpSOalAQBshkncbIdQybqU0tpZEsA0aUnBJCGES52RoLNI9Fmb0vp_SBqDMmvAMYu3xsTHyFAmYsw5tzKmij5ZKzVlrPWRtTaKLui7D2PsA4h3DtIygadM653zhYigtdG4tw7oonuo8WZTznkvVedjj5nyvjfRRX8_5ALAZA6BZN7wACUKjQB_OWa8614J5WCE9MRP0AYgwoKUWgjBWAcAsTIzG2N5Ek2yfwYQ4gkpKOZmzLmPNslyEUMoAplBNEqw1jrA2xttBmwaRoHQgQ-qUEMdjYxfsg5hyyWoEwZgkpWOznnGO2TrB2AcFUhxTc26d2Wa4dwngWkjzHh4heK8pneF8P4QZwZeC-IvtfW-DTQjhCSkEgBICIENOiLECI20eQzSYviJ4ETME5hmHmY8lJfTyQgAeESV4eS-goWuMQ3C9ShhmPFKERBqF6nwGyGkpRbhLkamAJaxCiikP9IGZJVJ9hHFOBGVFZpqRgBEE2CA2AhwUCyDErINcWRLg6D5FlWYigwsPMhCaZKowsqpaCFCpUlp1kpFuESYIexwRVJMMVsKCw4p5KeDEmIdyzlgNOF4ABuIAA)

`visualMap-piecewise.categories` may generates a long controller, but I cannot find a way to make it scrollable or layout into multi-line.

### What does the proposed API look like?

Like the `legend`

### Workaround
[demo](https://echarts.apache.org/examples/zh/editor.html?c=line-simple&code=PYBwLglsB2AEC8sDeAoWsDGwA2wBOAXLANprqwDkAxACwDMA7AJwDCAohQDRnrVNMAhABwAxAIxcelKiICCAEQGNJ5aSJZCAbAAYATCvLURchjSEHeVBroEBWNgIvSGQlvLbyn1WSyay2-tyqRj50miJeMvIMIjEUZAC6QbAAnrIAHhAAzkSoqmApIACmRBQAbgCG2ACuRU4gwFkQkDCl2EUAZmBOFZlZADIVAEZF2LlS6AAWEAAmRQDyZUV42BUgRGB4tcmqHTBgAMoQAF4lsGJiO-RZk8AA7htbRVIAvlc394-1ZG9k6RnZcb5QpnCgYCpgIoAc3wKXqjWaUGgpSGwDAYGAAFsnB8HrBNtspL1soMRmNkBNYHtoIcTmcLq8fsksssIEUciQpHlVPiQSiKngnOgWe0MJCZgBZYBzUqY6rYSAgdpC2BFTEgSYVJoc7k82DNNUHArtIF68igCoYZopIjaAB0TEp6BelN-epFRTFpr1BsxRpSJopZvNIEt1qIlyd5FReDmeAAKnzKFkcLMVaoY3GAOqzMCTIi6KNus2rMnes0Wq0FCNF11XdDQCqY0GAN7TAHSqgHe5FVFaBYGVBs02khiJJR9JEYjaBKu15XXXkRvN0q2bRQwCnpoAac0AjFaARqDABNugDLbQDctoASgMAOOkqgrFUoYapZDHY-v6yF-41neeqLC4QjSejMdjxHqLqqMW6AfrAi6grYTDaJi2CAIuJgDGPoA-K6AL1Gl5JmCd4Piqvr-oG4HoF--ClFQ_DCOIgE8sB5CgQOqiQaUNC6KugCGIYAICGAK4OgBumoAkT4YdelC3veWK4S--HvlGxE_iEijKDOIFzpSjGUIAvpqAOKagBuGapgAr5oAQAmAB1-gD8OoAJxEAFSALRygCAHiugDiTgJoLCThT54W-5afjgJFqBoOj6AptFKXqKkUCusHYIAmTaAMXagBXqYAerGACVGgBOQYA6LaAIvKgBM6Q5N7YaJLniW59E8tJpHGLIpjmP5zqBTywWAJmZgD0doASga1YAsPKAINygAQ5oAPplZUJOWPpSrkBpJwbFc4Nj2I4lWwHR4HBYA-w4ALSAJHOgBVdvNgBfioAx8qAKMRvVYSJA0-vlw3ueQY3UC4bgeFRIGzlyylNqCgD2wYtYiroA7fqAL9qgADnoA5R6ACZpgAlroA8YH7U5uWDSdBFSZ5MlUD4fgBLdtH3aoc1PaUtWAGCBgBiMYtgClQYAxfE7sh4P9WJhoFYRmBwyVoThCjzpo-QGNLpQgDMaYAkoqAGzBgAImYAocqAAfmgA1VoAiDqADiu5OHZTr6nYVHnfiV0SxBE000aO6BQngszlhi6ywEIVztF0RBG1IOtQpMYBm1cqLoliRCaObHk0hUEDQKSoxfM8VVkBiOCKnrltQsspTElkThYNAHQe2cBJFFcEcAArAB7kI_uBV6gtAMB1Czwq3HiCdMmQQxbDcevADgqLjiQFB4J63TTn76AB9gtflriRAdFULKl1reBrNMGATprsAzBCWpFDbnLo5SKbVHgGBFAAEkUFRxj3feJ5SMwQM20BNDAHKkMGNPoB0MwAJIzKUvYdEwRRMHQQhMEIGAzBgNCaGIzBDAwbQz8aDpgXJjSggAxVUAIMqgAwJUAN4-oC26YXwPvRs2BEGwGOHnRMgkG73CZgFKMF8ILgIoO2LsT5dj4ExBCXIdE9TZ1KB0XAEIMFYOgEUHBoJmybAgBgAhrczTEOCtAwAsCqAAfPDBew8A0NnkgehPJGGUBQR7KobDsGYWkgIOEtY9Tj1UIvZeZwz5mmIBQQAaMqADDNBBnBzhmBXLYkKq5Ny7kPKeC8-ieRmMABXKgB-I0ALKJgBM0y4LATQuhdCOOgmFJCaEKCeNUGYviNjDb0DoI45ibEuJ8TiZQ-ugBwzUAD56gAKVygSE96dAHFqS0rpQyplLI2W0PZeJ5AzFrhKcksQdBtAMFsJE7QYUopxSSmlTKzT0BmO6sk3QZgaCOIas1dq3UclRjMfNQASokdN0H_XplAlprU2rtZZwYzHPSgR0hg1gdkUFeu9KE31_rAzBmM-ugB9jLOSEip2g6C6DtFcnG-NiakyOaYiggA7TMCR0962hHHc35sLcWUsW48k8RrZIZRsjVCqBKNYE4HoMMwiANkK87jZDqE-feh9j7IlgBEyk4JIQwh1uyXFwYnHrm3PuY855QEhRgnBGJ6FckUAyVCDiPF-JCo0tpfSxlzLWTsjy0KcFBkJRShlHl8zWqdR6kKvZ61tp7SFTcz6v1Aagw1XjQmJMyZCthYLUWksCHNI9gAJQqNAUOZ0iJ0wVjyNlLjOXuIoKRP8rAOC5N4FE_lKF0KkXIqICQEbKAirFdk-mckGAYIoFKmpsr6kKpKj5PQWalURRiqqkZwa1AmDMBgzViyuqkWsHYBwWa9UHL2k21w7hPBJuuW9E1DzzWkURv4QIUZeD_KtUC-mLAwgRCTXa-FktlYxDiLo6iT5u5Uh3lu1k7Jr7QDmHXScSLmboHHu0UOR7yx8NaEJCAy9lRXCURQLIGA8A4HQe8IuPsri-hzDMPMtspC-nXhAK2s8XbkF9AAcRxecWlqhQwzFQVCIgvSpD4DZDSe-ecnCQnSIcamlJqS0lOBGJDPIyMiCbBAbAQ433uqyItFkOsOgqjI1mIoEHrZ4ZkWop8ZGJL8ZoeggusATazzBD2DOThJg8cgxhzDGY0QPhA6oSeYAKgsr9SudlriuUXifLy6JMaVTCpYqKrJErKTZuqTKup8rGkWdLSq4Z6qTP1u1RZ9tBqLPGruaax5Fmp2AptXZpdDqpZSCRS6F4ABuIAA)
you can also listen the `legendselectchanged` events and sync `selected` to the `visualMap`